diff --git a/smtpd/datastore.go b/datastore/datastore.go
similarity index 92%
rename from smtpd/datastore.go
rename to datastore/datastore.go
index 180a3ec..67aebf6 100644
--- a/smtpd/datastore.go
+++ b/datastore/datastore.go
@@ -1,4 +1,5 @@
-package smtpd
+// Package datastore contains implementation independent datastore logic
+package datastore
 
 import (
 	"errors"
diff --git a/smtpd/retention.go b/datastore/retention.go
similarity index 93%
rename from smtpd/retention.go
rename to datastore/retention.go
index 79c28b5..7d52c27 100644
--- a/smtpd/retention.go
+++ b/datastore/retention.go
@@ -1,4 +1,4 @@
-package smtpd
+package datastore
 
 import (
 	"container/list"
@@ -36,6 +36,11 @@ func init() {
 	rm.Set("Period", expRetentionPeriod)
 	rm.Set("RetainedHist", expRetainedHist)
 	rm.Set("RetainedCurrent", expRetainedCurrent)
+
+	log.AddTickerFunc(func() {
+		expRetentionDeletesHist.Set(log.PushMetric(retentionDeletesHist, expRetentionDeletesTotal))
+		expRetainedHist.Set(log.PushMetric(retainedHist, expRetainedCurrent))
+	})
 }
 
 // RetentionScanner looks for messages older than the configured retention period and deletes them.
@@ -85,9 +90,9 @@ retentionLoop:
 			dur := time.Minute - since
 			log.Tracef("Retention scanner sleeping for %v", dur)
 			select {
-			case _ = <-rs.globalShutdown:
+			case <-rs.globalShutdown:
 				break retentionLoop
-			case _ = <-time.After(dur):
+			case <-time.After(dur):
 			}
 		}
 		// Kickoff scan
@@ -97,7 +102,7 @@ retentionLoop:
 		}
 		// Check for global shutdown
 		select {
-		case _ = <-rs.globalShutdown:
+		case <-rs.globalShutdown:
 			break retentionLoop
 		default:
 		}
@@ -154,9 +159,7 @@ func (rs *RetentionScanner) doScan() error {
 // Join does not retun until the retention scanner has shut down
 func (rs *RetentionScanner) Join() {
 	if rs.retentionShutdown != nil {
-		select {
-		case <-rs.retentionShutdown:
-		}
+		<-rs.retentionShutdown
 	}
 }
 
diff --git a/datastore/retention_test.go b/datastore/retention_test.go
new file mode 100644
index 0000000..c357f7e
--- /dev/null
+++ b/datastore/retention_test.go
@@ -0,0 +1,67 @@
+package datastore
+
+import (
+	"fmt"
+	"testing"
+	"time"
+)
+
+func TestDoRetentionScan(t *testing.T) {
+	// Create mock objects
+	mds := &MockDataStore{}
+
+	mb1 := &MockMailbox{}
+	mb2 := &MockMailbox{}
+	mb3 := &MockMailbox{}
+
+	// Mockup some different aged messages (num is in hours)
+	new1 := mockMessage(0)
+	new2 := mockMessage(1)
+	new3 := mockMessage(2)
+	old1 := mockMessage(4)
+	old2 := mockMessage(12)
+	old3 := mockMessage(24)
+
+	// First it should ask for all mailboxes
+	mds.On("AllMailboxes").Return([]Mailbox{mb1, mb2, mb3}, nil)
+
+	// Then for all messages on each box
+	mb1.On("GetMessages").Return([]Message{new1, old1, old2}, nil)
+	mb2.On("GetMessages").Return([]Message{old3, new2}, nil)
+	mb3.On("GetMessages").Return([]Message{new3}, nil)
+
+	// Test 4 hour retention
+	rs := &RetentionScanner{
+		ds:              mds,
+		retentionPeriod: 4*time.Hour - time.Minute,
+		retentionSleep:  0,
+	}
+	if err := rs.doScan(); err != nil {
+		t.Error(err)
+	}
+
+	// Check our assertions
+	mds.AssertExpectations(t)
+	mb1.AssertExpectations(t)
+	mb2.AssertExpectations(t)
+	mb3.AssertExpectations(t)
+
+	// Delete should not have been called on new messages
+	new1.AssertNotCalled(t, "Delete")
+	new2.AssertNotCalled(t, "Delete")
+	new3.AssertNotCalled(t, "Delete")
+
+	// Delete should have been called once on old messages
+	old1.AssertNumberOfCalls(t, "Delete", 1)
+	old2.AssertNumberOfCalls(t, "Delete", 1)
+	old3.AssertNumberOfCalls(t, "Delete", 1)
+}
+
+// Make a MockMessage of a specific age
+func mockMessage(ageHours int) *MockMessage {
+	msg := &MockMessage{}
+	msg.On("ID").Return(fmt.Sprintf("MSG[age=%vh]", ageHours))
+	msg.On("Date").Return(time.Now().Add(time.Duration(ageHours*-1) * time.Hour))
+	msg.On("Delete").Return(nil)
+	return msg
+}
diff --git a/rest/testmocks_test.go b/datastore/testing.go
similarity index 62%
rename from rest/testmocks_test.go
rename to datastore/testing.go
index bc720fc..23474f6 100644
--- a/rest/testmocks_test.go
+++ b/datastore/testing.go
@@ -1,4 +1,4 @@
-package rest
+package datastore
 
 import (
 	"io"
@@ -6,130 +6,151 @@ import (
 	"time"
 
 	"github.com/jhillyerd/enmime"
-	"github.com/jhillyerd/inbucket/smtpd"
 	"github.com/stretchr/testify/mock"
 )
 
-// Mock DataStore object
+// MockDataStore is a shared mock for unit testing
 type MockDataStore struct {
 	mock.Mock
 }
 
-func (m *MockDataStore) MailboxFor(name string) (smtpd.Mailbox, error) {
+// MailboxFor mock function
+func (m *MockDataStore) MailboxFor(name string) (Mailbox, error) {
 	args := m.Called(name)
-	return args.Get(0).(smtpd.Mailbox), args.Error(1)
+	return args.Get(0).(Mailbox), args.Error(1)
 }
 
-func (m *MockDataStore) AllMailboxes() ([]smtpd.Mailbox, error) {
+// AllMailboxes mock function
+func (m *MockDataStore) AllMailboxes() ([]Mailbox, error) {
 	args := m.Called()
-	return args.Get(0).([]smtpd.Mailbox), args.Error(1)
+	return args.Get(0).([]Mailbox), args.Error(1)
 }
 
-// Mock Mailbox object
+// MockMailbox is a shared mock for unit testing
 type MockMailbox struct {
 	mock.Mock
 }
 
-func (m *MockMailbox) GetMessages() ([]smtpd.Message, error) {
+// GetMessages mock function
+func (m *MockMailbox) GetMessages() ([]Message, error) {
 	args := m.Called()
-	return args.Get(0).([]smtpd.Message), args.Error(1)
+	return args.Get(0).([]Message), args.Error(1)
 }
 
-func (m *MockMailbox) GetMessage(id string) (smtpd.Message, error) {
+// GetMessage mock function
+func (m *MockMailbox) GetMessage(id string) (Message, error) {
 	args := m.Called(id)
-	return args.Get(0).(smtpd.Message), args.Error(1)
+	return args.Get(0).(Message), args.Error(1)
 }
 
+// Purge mock function
 func (m *MockMailbox) Purge() error {
 	args := m.Called()
 	return args.Error(0)
 }
 
-func (m *MockMailbox) NewMessage() (smtpd.Message, error) {
+// NewMessage mock function
+func (m *MockMailbox) NewMessage() (Message, error) {
 	args := m.Called()
-	return args.Get(0).(smtpd.Message), args.Error(1)
+	return args.Get(0).(Message), args.Error(1)
 }
 
+// Name mock function
 func (m *MockMailbox) Name() string {
 	args := m.Called()
 	return args.String(0)
 }
 
+// String mock function
 func (m *MockMailbox) String() string {
 	args := m.Called()
 	return args.String(0)
 }
 
-// Mock Message object
+// MockMessage is a shared mock for unit testing
 type MockMessage struct {
 	mock.Mock
 }
 
+// ID mock function
 func (m *MockMessage) ID() string {
 	args := m.Called()
 	return args.String(0)
 }
 
+// From mock function
 func (m *MockMessage) From() string {
 	args := m.Called()
 	return args.String(0)
 }
 
+// To mock function
 func (m *MockMessage) To() []string {
 	args := m.Called()
 	return args.Get(0).([]string)
 }
 
+// Date mock function
 func (m *MockMessage) Date() time.Time {
 	args := m.Called()
 	return args.Get(0).(time.Time)
 }
 
+// Subject mock function
 func (m *MockMessage) Subject() string {
 	args := m.Called()
 	return args.String(0)
 }
 
+// ReadHeader mock function
 func (m *MockMessage) ReadHeader() (msg *mail.Message, err error) {
 	args := m.Called()
 	return args.Get(0).(*mail.Message), args.Error(1)
 }
 
+// ReadBody mock function
 func (m *MockMessage) ReadBody() (body *enmime.Envelope, err error) {
 	args := m.Called()
 	return args.Get(0).(*enmime.Envelope), args.Error(1)
 }
 
+// ReadRaw mock function
 func (m *MockMessage) ReadRaw() (raw *string, err error) {
 	args := m.Called()
 	return args.Get(0).(*string), args.Error(1)
 }
 
+// RawReader mock function
 func (m *MockMessage) RawReader() (reader io.ReadCloser, err error) {
 	args := m.Called()
 	return args.Get(0).(io.ReadCloser), args.Error(1)
 }
 
+// Size mock function
 func (m *MockMessage) Size() int64 {
 	args := m.Called()
 	return int64(args.Int(0))
 }
 
+// Append mock function
 func (m *MockMessage) Append(data []byte) error {
 	// []byte arg seems to mess up testify/mock
 	return nil
 }
 
+// Close mock function
 func (m *MockMessage) Close() error {
 	args := m.Called()
 	return args.Error(0)
 }
 
+// Delete mock function
 func (m *MockMessage) Delete() error {
 	args := m.Called()
 	return args.Error(0)
 }
 
+// String mock function
 func (m *MockMessage) String() string {
 	args := m.Called()
 	return args.String(0)
diff --git a/smtpd/filemsg.go b/filestore/fmessage.go
similarity index 96%
rename from smtpd/filemsg.go
rename to filestore/fmessage.go
index edf3ec9..54da127 100644
--- a/smtpd/filemsg.go
+++ b/filestore/fmessage.go
@@ -1,4 +1,4 @@
-package smtpd
+package filestore
 
 import (
 	"bufio"
@@ -11,6 +11,7 @@ import (
 	"time"
 
 	"github.com/jhillyerd/enmime"
+	"github.com/jhillyerd/inbucket/datastore"
 	"github.com/jhillyerd/inbucket/log"
 )
 
@@ -33,7 +34,7 @@ type FileMessage struct {
 
 // NewMessage creates a new FileMessage object and sets the Date and Id fields.
 // It will also delete messages over messageCap if configured.
-func (mb *FileMailbox) NewMessage() (Message, error) {
+func (mb *FileMailbox) NewMessage() (datastore.Message, error) {
 	// Load index
 	if !mb.indexLoaded {
 		if err := mb.readIndex(); err != nil {
@@ -71,7 +72,7 @@ func (m *FileMessage) From() string {
 	return m.Ffrom
 }
 
-// From returns the value of the Message To header
+// To returns the value of the Message To header
 func (m *FileMessage) To() []string {
 	return m.Fto
 }
@@ -165,7 +166,7 @@ func (m *FileMessage) ReadRaw() (raw *string, err error) {
 func (m *FileMessage) Append(data []byte) error {
 	// Prevent Appending to a pre-existing Message
 	if !m.writable {
-		return ErrNotWritable
+		return datastore.ErrNotWritable
 	}
 	// Open file for writing if we haven't yet
 	if m.writer == nil {
diff --git a/smtpd/filestore.go b/filestore/fstore.go
similarity index 89%
rename from smtpd/filestore.go
rename to filestore/fstore.go
index 9f8f615..4ac7bc1 100644
--- a/smtpd/filestore.go
+++ b/filestore/fstore.go
@@ -1,4 +1,4 @@
-package smtpd
+package filestore
 
 import (
 	"bufio"
@@ -12,7 +12,9 @@ import (
 	"time"
 
 	"github.com/jhillyerd/inbucket/config"
+	"github.com/jhillyerd/inbucket/datastore"
 	"github.com/jhillyerd/inbucket/log"
+	"github.com/jhillyerd/inbucket/stringutil"
 )
 
 // Name of index file in each mailbox
@@ -55,7 +57,7 @@ type FileDataStore struct {
 }
 
 // NewFileDataStore creates a new DataStore object using the specified path
-func NewFileDataStore(cfg config.DataStoreConfig) DataStore {
+func NewFileDataStore(cfg config.DataStoreConfig) datastore.DataStore {
 	path := cfg.Path
 	if path == "" {
 		log.Errorf("No value configured for datastore path")
@@ -73,19 +75,19 @@ func NewFileDataStore(cfg config.DataStoreConfig) DataStore {
 
 // DefaultFileDataStore creates a new DataStore object.  It uses the inbucket.Config object to
 // construct it's path.
-func DefaultFileDataStore() DataStore {
+func DefaultFileDataStore() datastore.DataStore {
 	cfg := config.GetDataStoreConfig()
 	return NewFileDataStore(cfg)
 }
 
 // MailboxFor retrieves the Mailbox object for a specified email address, if the mailbox
 // does not exist, it will attempt to create it.
-func (ds *FileDataStore) MailboxFor(emailAddress string) (Mailbox, error) {
-	name, err := ParseMailboxName(emailAddress)
+func (ds *FileDataStore) MailboxFor(emailAddress string) (datastore.Mailbox, error) {
+	name, err := stringutil.ParseMailboxName(emailAddress)
 	if err != nil {
 		return nil, err
 	}
-	dir := HashMailboxName(name)
+	dir := stringutil.HashMailboxName(name)
 	s1 := dir[0:3]
 	s2 := dir[0:6]
 	path := filepath.Join(ds.mailPath, s1, s2, dir)
@@ -96,8 +98,8 @@ func (ds *FileDataStore) MailboxFor(emailAddress string) (Mailbox, error) {
 }
 
 // AllMailboxes returns a slice with all Mailboxes
-func (ds *FileDataStore) AllMailboxes() ([]Mailbox, error) {
-	mailboxes := make([]Mailbox, 0, 100)
+func (ds *FileDataStore) AllMailboxes() ([]datastore.Mailbox, error) {
+	mailboxes := make([]datastore.Mailbox, 0, 100)
 	infos1, err := ioutil.ReadDir(ds.mailPath)
 	if err != nil {
 		return nil, err
@@ -149,24 +151,26 @@ type FileMailbox struct {
 	messages    []*FileMessage
 }
 
+// Name of the mailbox
 func (mb *FileMailbox) Name() string {
 	return mb.name
 }
 
+// String renders the name and directory path of the mailbox
 func (mb *FileMailbox) String() string {
 	return mb.name + "[" + mb.dirName + "]"
 }
 
 // GetMessages scans the mailbox directory for .gob files and decodes them into
 // a slice of Message objects.
-func (mb *FileMailbox) GetMessages() ([]Message, error) {
+func (mb *FileMailbox) GetMessages() ([]datastore.Message, error) {
 	if !mb.indexLoaded {
 		if err := mb.readIndex(); err != nil {
 			return nil, err
 		}
 	}
 
-	messages := make([]Message, len(mb.messages))
+	messages := make([]datastore.Message, len(mb.messages))
 	for i, m := range mb.messages {
 		messages[i] = m
 	}
@@ -174,7 +178,7 @@ func (mb *FileMailbox) GetMessages() ([]Message, error) {
 }
 
 // GetMessage decodes a single message by Id and returns a Message object
-func (mb *FileMailbox) GetMessage(id string) (Message, error) {
+func (mb *FileMailbox) GetMessage(id string) (datastore.Message, error) {
 	if !mb.indexLoaded {
 		if err := mb.readIndex(); err != nil {
 			return nil, err
@@ -183,15 +187,15 @@ func (mb *FileMailbox) GetMessage(id string) (Message, error) {
 
 	if id == "latest" && len(mb.messages) != 0 {
 		return mb.messages[len(mb.messages)-1], nil
-	} else {
-		for _, m := range mb.messages {
-			if m.Fid == id {
-				return m, nil
-			}
+	}
+
+	for _, m := range mb.messages {
+		if m.Fid == id {
+			return m, nil
 		}
 	}
 
-	return nil, ErrNotExist
+	return nil, datastore.ErrNotExist
 }
 
 // Purge deletes all messages in this mailbox
diff --git a/smtpd/filestore_test.go b/filestore/fstore_test.go
similarity index 99%
rename from smtpd/filestore_test.go
rename to filestore/fstore_test.go
index 2ca3104..9cac985 100644
--- a/smtpd/filestore_test.go
+++ b/filestore/fstore_test.go
@@ -1,4 +1,4 @@
-package smtpd
+package filestore
 
 import (
 	"bytes"
@@ -470,8 +470,8 @@ func TestGetLatestMessage(t *testing.T) {
 	mb, err := ds.MailboxFor(mbName)
 	assert.Nil(t, err)
 	msg, err := mb.GetMessage("latest")
+	assert.Nil(t, msg)
 	assert.Error(t, err)
-	fmt.Println(msg)
 
 	// Deliver test message
 	deliverMessage(ds, mbName, "test", time.Now())
@@ -496,7 +496,7 @@ func TestGetLatestMessage(t *testing.T) {
 	assert.True(t, msg.ID() == id3, "Expected %q to be equal to %q", msg.ID(), id3)
 
 	// Test wrong id
-	msg, err = mb.GetMessage("wrongid")
+	_, err = mb.GetMessage("wrongid")
 	assert.Error(t, err)
 
 	if t.Failed() {
diff --git a/httpd/context.go b/httpd/context.go
index 52abfc6..6a54541 100644
--- a/httpd/context.go
+++ b/httpd/context.go
@@ -7,15 +7,15 @@ import (
 	"github.com/gorilla/mux"
 	"github.com/gorilla/sessions"
 	"github.com/jhillyerd/inbucket/config"
+	"github.com/jhillyerd/inbucket/datastore"
 	"github.com/jhillyerd/inbucket/msghub"
-	"github.com/jhillyerd/inbucket/smtpd"
 )
 
 // Context is passed into every request handler function
 type Context struct {
 	Vars      map[string]string
 	Session   *sessions.Session
-	DataStore smtpd.DataStore
+	DataStore datastore.DataStore
 	MsgHub    *msghub.Hub
 	WebConfig config.WebConfig
 	IsJSON    bool
diff --git a/httpd/server.go b/httpd/server.go
index 103e0f1..f89b9ff 100644
--- a/httpd/server.go
+++ b/httpd/server.go
@@ -13,9 +13,9 @@ import (
 	"github.com/gorilla/securecookie"
 	"github.com/gorilla/sessions"
 	"github.com/jhillyerd/inbucket/config"
+	"github.com/jhillyerd/inbucket/datastore"
 	"github.com/jhillyerd/inbucket/log"
 	"github.com/jhillyerd/inbucket/msghub"
-	"github.com/jhillyerd/inbucket/smtpd"
 )
 
 // Handler is a function type that handles an HTTP request in Inbucket
@@ -23,7 +23,7 @@ type Handler func(http.ResponseWriter, *http.Request, *Context) error
 
 var (
 	// DataStore is where all the mailboxes and messages live
-	DataStore smtpd.DataStore
+	DataStore datastore.DataStore
 
 	// msgHub holds a reference to the message pub/sub system
 	msgHub *msghub.Hub
@@ -51,7 +51,7 @@ func init() {
 func Initialize(
 	cfg config.WebConfig,
 	shutdownChan chan bool,
-	ds smtpd.DataStore,
+	ds datastore.DataStore,
 	mh *msghub.Hub) {
 
 	webConfig = cfg
diff --git a/inbucket.go b/inbucket.go
index 7593000..83c39f4 100644
--- a/inbucket.go
+++ b/inbucket.go
@@ -13,6 +13,7 @@ import (
 	"time"
 
 	"github.com/jhillyerd/inbucket/config"
+	"github.com/jhillyerd/inbucket/filestore"
 	"github.com/jhillyerd/inbucket/httpd"
 	"github.com/jhillyerd/inbucket/log"
 	"github.com/jhillyerd/inbucket/msghub"
@@ -115,7 +116,7 @@ func main() {
 	msgHub := msghub.New(rootCtx, config.GetWebConfig().MonitorHistory)
 
 	// Grab our datastore
-	ds := smtpd.DefaultFileDataStore()
+	ds := filestore.DefaultFileDataStore()
 
 	// Start HTTP server
 	httpd.Initialize(config.GetWebConfig(), shutdownChan, ds, msgHub)
diff --git a/log/metrics.go b/log/metrics.go
new file mode 100644
index 0000000..c16f1e8
--- /dev/null
+++ b/log/metrics.go
@@ -0,0 +1,62 @@
+package log
+
+import (
+	"container/list"
+	"expvar"
+	"strings"
+	"time"
+)
+
+// TickerFunc is the type of metrics function accepted by AddTickerFunc
+type TickerFunc func()
+
+var tickerFuncChan = make(chan TickerFunc)
+
+func init() {
+	go metricsTicker()
+}
+
+// AddTickerFunc adds a new function callback to the list of metrics TickerFuncs that get
+// called each minute.
+func AddTickerFunc(f TickerFunc) {
+	tickerFuncChan <- f
+}
+
+// PushMetric adds the metric to the end of the list and returns a comma separated string of the
+// previous 61 entries.  We return 61 instead of 60 (an hour) because the chart on the client
+// tracks deltas between these values - there is nothing to compare the first value against.
+func PushMetric(history *list.List, ev expvar.Var) string {
+	history.PushBack(ev.String())
+	if history.Len() > 61 {
+		history.Remove(history.Front())
+	}
+	return joinStringList(history)
+}
+
+// joinStringList joins a List containing strings by commas
+func joinStringList(listOfStrings *list.List) string {
+	if listOfStrings.Len() == 0 {
+		return ""
+	}
+	s := make([]string, 0, listOfStrings.Len())
+	for e := listOfStrings.Front(); e != nil; e = e.Next() {
+		s = append(s, e.Value.(string))
+	}
+	return strings.Join(s, ",")
+}
+
+func metricsTicker() {
+	funcs := make([]TickerFunc, 0)
+	ticker := time.NewTicker(time.Minute)
+
+	for {
+		select {
+		case <-ticker.C:
+			for _, f := range funcs {
+				f()
+			}
+		case f := <-tickerFuncChan:
+			funcs = append(funcs, f)
+		}
+	}
+}
diff --git a/pop3d/handler.go b/pop3d/handler.go
index 782cf8e..7f5967e 100644
--- a/pop3d/handler.go
+++ b/pop3d/handler.go
@@ -11,8 +11,8 @@ import (
 	"strings"
 	"time"
 
+	"github.com/jhillyerd/inbucket/datastore"
 	"github.com/jhillyerd/inbucket/log"
-	"github.com/jhillyerd/inbucket/smtpd"
 )
 
 // State tracks the current mode of our POP3 state machine
@@ -57,18 +57,18 @@ var commands = map[string]bool{
 
 // Session defines an active POP3 session
 type Session struct {
-	server     *Server         // Reference to the server we belong to
-	id         int             // Session ID number
-	conn       net.Conn        // Our network connection
-	remoteHost string          // IP address of client
-	sendError  error           // Used to bail out of read loop on send error
-	state      State           // Current session state
-	reader     *bufio.Reader   // Buffered reader for our net conn
-	user       string          // Mailbox name
-	mailbox    smtpd.Mailbox   // Mailbox instance
-	messages   []smtpd.Message // Slice of messages in mailbox
-	retain     []bool          // Messages to retain upon UPDATE (true=retain)
-	msgCount   int             // Number of undeleted messages
+	server     *Server             // Reference to the server we belong to
+	id         int                 // Session ID number
+	conn       net.Conn            // Our network connection
+	remoteHost string              // IP address of client
+	sendError  error               // Used to bail out of read loop on send error
+	state      State               // Current session state
+	reader     *bufio.Reader       // Buffered reader for our net conn
+	user       string              // Mailbox name
+	mailbox    datastore.Mailbox   // Mailbox instance
+	messages   []datastore.Message // Slice of messages in mailbox
+	retain     []bool              // Messages to retain upon UPDATE (true=retain)
+	msgCount   int                 // Number of undeleted messages
 }
 
 // NewSession creates a new POP3 session
@@ -432,7 +432,7 @@ func (ses *Session) transactionHandler(cmd string, args []string) {
 }
 
 // Send the contents of the message to the client
-func (ses *Session) sendMessage(msg smtpd.Message) {
+func (ses *Session) sendMessage(msg datastore.Message) {
 	reader, err := msg.RawReader()
 	if err != nil {
 		ses.logError("Failed to read message for RETR command")
@@ -465,7 +465,7 @@ func (ses *Session) sendMessage(msg smtpd.Message) {
 }
 
 // Send the headers plus the top N lines to the client
-func (ses *Session) sendMessageTop(msg smtpd.Message, lineCount int) {
+func (ses *Session) sendMessageTop(msg datastore.Message, lineCount int) {
 	reader, err := msg.RawReader()
 	if err != nil {
 		ses.logError("Failed to read message for RETR command")
diff --git a/pop3d/listener.go b/pop3d/listener.go
index d1b11d5..58b0d82 100644
--- a/pop3d/listener.go
+++ b/pop3d/listener.go
@@ -8,8 +8,8 @@ import (
 	"time"
 
 	"github.com/jhillyerd/inbucket/config"
+	"github.com/jhillyerd/inbucket/datastore"
 	"github.com/jhillyerd/inbucket/log"
-	"github.com/jhillyerd/inbucket/smtpd"
 )
 
 // Server defines an instance of our POP3 server
@@ -17,14 +17,14 @@ type Server struct {
 	host           string
 	domain         string
 	maxIdleSeconds int
-	dataStore      smtpd.DataStore
+	dataStore      datastore.DataStore
 	listener       net.Listener
 	globalShutdown chan bool
 	waitgroup      *sync.WaitGroup
 }
 
 // New creates a new Server struct
-func New(cfg config.POP3Config, shutdownChan chan bool, ds smtpd.DataStore) *Server {
+func New(cfg config.POP3Config, shutdownChan chan bool, ds datastore.DataStore) *Server {
 	return &Server{
 		host:           fmt.Sprintf("%v:%v", cfg.IP4address, cfg.IP4port),
 		domain:         cfg.Domain,
diff --git a/rest/apiv1_controller.go b/rest/apiv1_controller.go
index 67a3528..9037eb1 100644
--- a/rest/apiv1_controller.go
+++ b/rest/apiv1_controller.go
@@ -10,16 +10,17 @@ import (
 	"io/ioutil"
 	"strconv"
 
+	"github.com/jhillyerd/inbucket/datastore"
 	"github.com/jhillyerd/inbucket/httpd"
 	"github.com/jhillyerd/inbucket/log"
 	"github.com/jhillyerd/inbucket/rest/model"
-	"github.com/jhillyerd/inbucket/smtpd"
+	"github.com/jhillyerd/inbucket/stringutil"
 )
 
 // MailboxListV1 renders a list of messages in a mailbox
 func MailboxListV1(w http.ResponseWriter, req *http.Request, ctx *httpd.Context) (err error) {
 	// Don't have to validate these aren't empty, Gorilla returns 404
-	name, err := smtpd.ParseMailboxName(ctx.Vars["name"])
+	name, err := stringutil.ParseMailboxName(ctx.Vars["name"])
 	if err != nil {
 		return err
 	}
@@ -54,7 +55,7 @@ func MailboxListV1(w http.ResponseWriter, req *http.Request, ctx *httpd.Context)
 func MailboxShowV1(w http.ResponseWriter, req *http.Request, ctx *httpd.Context) (err error) {
 	// Don't have to validate these aren't empty, Gorilla returns 404
 	id := ctx.Vars["id"]
-	name, err := smtpd.ParseMailboxName(ctx.Vars["name"])
+	name, err := stringutil.ParseMailboxName(ctx.Vars["name"])
 	if err != nil {
 		return err
 	}
@@ -64,7 +65,7 @@ func MailboxShowV1(w http.ResponseWriter, req *http.Request, ctx *httpd.Context)
 		return fmt.Errorf("Failed to get mailbox for %q: %v", name, err)
 	}
 	msg, err := mb.GetMessage(id)
-	if err == smtpd.ErrNotExist {
+	if err == datastore.ErrNotExist {
 		http.NotFound(w, req)
 		return nil
 	}
@@ -116,7 +117,7 @@ func MailboxShowV1(w http.ResponseWriter, req *http.Request, ctx *httpd.Context)
 // MailboxPurgeV1 deletes all messages from a mailbox
 func MailboxPurgeV1(w http.ResponseWriter, req *http.Request, ctx *httpd.Context) (err error) {
 	// Don't have to validate these aren't empty, Gorilla returns 404
-	name, err := smtpd.ParseMailboxName(ctx.Vars["name"])
+	name, err := stringutil.ParseMailboxName(ctx.Vars["name"])
 	if err != nil {
 		return err
 	}
@@ -139,7 +140,7 @@ func MailboxPurgeV1(w http.ResponseWriter, req *http.Request, ctx *httpd.Context
 func MailboxSourceV1(w http.ResponseWriter, req *http.Request, ctx *httpd.Context) (err error) {
 	// Don't have to validate these aren't empty, Gorilla returns 404
 	id := ctx.Vars["id"]
-	name, err := smtpd.ParseMailboxName(ctx.Vars["name"])
+	name, err := stringutil.ParseMailboxName(ctx.Vars["name"])
 	if err != nil {
 		return err
 	}
@@ -149,7 +150,7 @@ func MailboxSourceV1(w http.ResponseWriter, req *http.Request, ctx *httpd.Contex
 		return fmt.Errorf("Failed to get mailbox for %q: %v", name, err)
 	}
 	message, err := mb.GetMessage(id)
-	if err == smtpd.ErrNotExist {
+	if err == datastore.ErrNotExist {
 		http.NotFound(w, req)
 		return nil
 	}
@@ -173,7 +174,7 @@ func MailboxSourceV1(w http.ResponseWriter, req *http.Request, ctx *httpd.Contex
 func MailboxDeleteV1(w http.ResponseWriter, req *http.Request, ctx *httpd.Context) (err error) {
 	// Don't have to validate these aren't empty, Gorilla returns 404
 	id := ctx.Vars["id"]
-	name, err := smtpd.ParseMailboxName(ctx.Vars["name"])
+	name, err := stringutil.ParseMailboxName(ctx.Vars["name"])
 	if err != nil {
 		return err
 	}
@@ -183,7 +184,7 @@ func MailboxDeleteV1(w http.ResponseWriter, req *http.Request, ctx *httpd.Contex
 		return fmt.Errorf("Failed to get mailbox for %q: %v", name, err)
 	}
 	message, err := mb.GetMessage(id)
-	if err == smtpd.ErrNotExist {
+	if err == datastore.ErrNotExist {
 		http.NotFound(w, req)
 		return nil
 	}
diff --git a/rest/apiv1_controller_test.go b/rest/apiv1_controller_test.go
index 9297f88..b1c9a00 100644
--- a/rest/apiv1_controller_test.go
+++ b/rest/apiv1_controller_test.go
@@ -9,7 +9,7 @@ import (
 	"testing"
 	"time"
 
-	"github.com/jhillyerd/inbucket/smtpd"
+	"github.com/jhillyerd/inbucket/datastore"
 )
 
 const (
@@ -31,7 +31,7 @@ const (
 
 func TestRestMailboxList(t *testing.T) {
 	// Setup
-	ds := &MockDataStore{}
+	ds := &datastore.MockDataStore{}
 	logbuf := setupWebServer(ds)
 
 	// Test invalid mailbox name
@@ -45,9 +45,9 @@ func TestRestMailboxList(t *testing.T) {
 	}
 
 	// Test empty mailbox
-	emptybox := &MockMailbox{}
+	emptybox := &datastore.MockMailbox{}
 	ds.On("MailboxFor", "empty").Return(emptybox, nil)
-	emptybox.On("GetMessages").Return([]smtpd.Message{}, nil)
+	emptybox.On("GetMessages").Return([]datastore.Message{}, nil)
 
 	w, err = testRestGet(baseURL + "/mailbox/empty")
 	expectCode = 200
@@ -59,7 +59,7 @@ func TestRestMailboxList(t *testing.T) {
 	}
 
 	// Test MailboxFor error
-	ds.On("MailboxFor", "error").Return(&MockMailbox{}, fmt.Errorf("Internal error"))
+	ds.On("MailboxFor", "error").Return(&datastore.MockMailbox{}, fmt.Errorf("Internal error"))
 	w, err = testRestGet(baseURL + "/mailbox/error")
 	expectCode = 500
 	if err != nil {
@@ -77,9 +77,9 @@ func TestRestMailboxList(t *testing.T) {
 	}
 
 	// Test MailboxFor error
-	error2box := &MockMailbox{}
+	error2box := &datastore.MockMailbox{}
 	ds.On("MailboxFor", "error2").Return(error2box, nil)
-	error2box.On("GetMessages").Return([]smtpd.Message{}, fmt.Errorf("Internal error 2"))
+	error2box.On("GetMessages").Return([]datastore.Message{}, fmt.Errorf("Internal error 2"))
 
 	w, err = testRestGet(baseURL + "/mailbox/error2")
 	expectCode = 500
@@ -107,11 +107,11 @@ func TestRestMailboxList(t *testing.T) {
 		Subject: "subject 2",
 		Date:    time.Date(2012, 7, 1, 10, 11, 12, 253, time.FixedZone("PDT", -700)),
 	}
-	goodbox := &MockMailbox{}
+	goodbox := &datastore.MockMailbox{}
 	ds.On("MailboxFor", "good").Return(goodbox, nil)
 	msg1 := data1.MockMessage()
 	msg2 := data2.MockMessage()
-	goodbox.On("GetMessages").Return([]smtpd.Message{msg1, msg2}, nil)
+	goodbox.On("GetMessages").Return([]datastore.Message{msg1, msg2}, nil)
 
 	// Check return code
 	w, err = testRestGet(baseURL + "/mailbox/good")
@@ -155,7 +155,7 @@ func TestRestMailboxList(t *testing.T) {
 
 func TestRestMessage(t *testing.T) {
 	// Setup
-	ds := &MockDataStore{}
+	ds := &datastore.MockDataStore{}
 	logbuf := setupWebServer(ds)
 
 	// Test invalid mailbox name
@@ -169,9 +169,9 @@ func TestRestMessage(t *testing.T) {
 	}
 
 	// Test requesting a message that does not exist
-	emptybox := &MockMailbox{}
+	emptybox := &datastore.MockMailbox{}
 	ds.On("MailboxFor", "empty").Return(emptybox, nil)
-	emptybox.On("GetMessage", "0001").Return(&MockMessage{}, smtpd.ErrNotExist)
+	emptybox.On("GetMessage", "0001").Return(&datastore.MockMessage{}, datastore.ErrNotExist)
 
 	w, err = testRestGet(baseURL + "/mailbox/empty/0001")
 	expectCode = 404
@@ -183,7 +183,7 @@ func TestRestMessage(t *testing.T) {
 	}
 
 	// Test MailboxFor error
-	ds.On("MailboxFor", "error").Return(&MockMailbox{}, fmt.Errorf("Internal error"))
+	ds.On("MailboxFor", "error").Return(&datastore.MockMailbox{}, fmt.Errorf("Internal error"))
 	w, err = testRestGet(baseURL + "/mailbox/error/0001")
 	expectCode = 500
 	if err != nil {
@@ -201,9 +201,9 @@ func TestRestMessage(t *testing.T) {
 	}
 
 	// Test GetMessage error
-	error2box := &MockMailbox{}
+	error2box := &datastore.MockMailbox{}
 	ds.On("MailboxFor", "error2").Return(error2box, nil)
-	error2box.On("GetMessage", "0001").Return(&MockMessage{}, fmt.Errorf("Internal error 2"))
+	error2box.On("GetMessage", "0001").Return(&datastore.MockMessage{}, fmt.Errorf("Internal error 2"))
 
 	w, err = testRestGet(baseURL + "/mailbox/error2/0001")
 	expectCode = 500
@@ -228,7 +228,7 @@ func TestRestMessage(t *testing.T) {
 		Text: "This is some text",
 		HTML: "This is some HTML",
 	}
-	goodbox := &MockMailbox{}
+	goodbox := &datastore.MockMailbox{}
 	ds.On("MailboxFor", "good").Return(goodbox, nil)
 	msg1 := data1.MockMessage()
 	goodbox.On("GetMessage", "0001").Return(msg1, nil)
diff --git a/rest/socketv1_controller.go b/rest/socketv1_controller.go
index 764519a..78bec2d 100644
--- a/rest/socketv1_controller.go
+++ b/rest/socketv1_controller.go
@@ -9,7 +9,7 @@ import (
 	"github.com/jhillyerd/inbucket/log"
 	"github.com/jhillyerd/inbucket/msghub"
 	"github.com/jhillyerd/inbucket/rest/model"
-	"github.com/jhillyerd/inbucket/smtpd"
+	"github.com/jhillyerd/inbucket/stringutil"
 )
 
 const (
@@ -169,7 +169,7 @@ func MonitorAllMessagesV1(
 
 func MonitorMailboxMessagesV1(
 	w http.ResponseWriter, req *http.Request, ctx *httpd.Context) (err error) {
-	name, err := smtpd.ParseMailboxName(ctx.Vars["name"])
+	name, err := stringutil.ParseMailboxName(ctx.Vars["name"])
 	if err != nil {
 		return err
 	}
diff --git a/rest/testutils_test.go b/rest/testutils_test.go
index 7cfd223..6ef4182 100644
--- a/rest/testutils_test.go
+++ b/rest/testutils_test.go
@@ -11,9 +11,9 @@ import (
 
 	"github.com/jhillyerd/enmime"
 	"github.com/jhillyerd/inbucket/config"
+	"github.com/jhillyerd/inbucket/datastore"
 	"github.com/jhillyerd/inbucket/httpd"
 	"github.com/jhillyerd/inbucket/msghub"
-	"github.com/jhillyerd/inbucket/smtpd"
 )
 
 type InputMessageData struct {
@@ -25,8 +25,8 @@ type InputMessageData struct {
 	HTML, Text                 string
 }
 
-func (d *InputMessageData) MockMessage() *MockMessage {
-	msg := &MockMessage{}
+func (d *InputMessageData) MockMessage() *datastore.MockMessage {
+	msg := &datastore.MockMessage{}
 	msg.On("ID").Return(d.ID)
 	msg.On("From").Return(d.From)
 	msg.On("To").Return(d.To)
@@ -188,7 +188,7 @@ func testRestGet(url string) (*httptest.ResponseRecorder, error) {
 	return w, nil
 }
 
-func setupWebServer(ds smtpd.DataStore) *bytes.Buffer {
+func setupWebServer(ds datastore.DataStore) *bytes.Buffer {
 	// Capture log output
 	buf := new(bytes.Buffer)
 	log.SetOutput(buf)
diff --git a/smtpd/handler.go b/smtpd/handler.go
index 7353194..f6c4397 100644
--- a/smtpd/handler.go
+++ b/smtpd/handler.go
@@ -12,8 +12,10 @@ import (
 	"strings"
 	"time"
 
+	"github.com/jhillyerd/inbucket/datastore"
 	"github.com/jhillyerd/inbucket/log"
 	"github.com/jhillyerd/inbucket/msghub"
+	"github.com/jhillyerd/inbucket/stringutil"
 )
 
 // State tracks the current mode of our SMTP state machine
@@ -71,7 +73,7 @@ var commands = map[string]bool{
 // recipientDetails for message delivery
 type recipientDetails struct {
 	address, localPart, domainPart string
-	mailbox                        Mailbox
+	mailbox                        datastore.Mailbox
 }
 
 // Session holds the state of an SMTP session
@@ -265,7 +267,7 @@ func (ss *Session) readyHandler(cmd string, arg string) {
 			return
 		}
 		from := m[1]
-		if _, _, err := ParseEmailAddress(from); err != nil {
+		if _, _, err := stringutil.ParseEmailAddress(from); err != nil {
 			ss.send("501 Bad sender address syntax")
 			ss.logWarn("Bad address as MAIL arg: %q, %s", from, err)
 			return
@@ -314,7 +316,7 @@ func (ss *Session) mailHandler(cmd string, arg string) {
 		}
 		// This trim is probably too forgiving
 		recip := strings.Trim(arg[3:], "<> ")
-		if _, _, err := ParseEmailAddress(recip); err != nil {
+		if _, _, err := stringutil.ParseEmailAddress(recip); err != nil {
 			ss.send("501 Bad recipient address syntax")
 			ss.logWarn("Bad address as RCPT arg: %q, %s", recip, err)
 			return
@@ -354,7 +356,7 @@ func (ss *Session) dataHandler() {
 	if ss.server.storeMessages {
 		for e := ss.recipients.Front(); e != nil; e = e.Next() {
 			recip := e.Value.(string)
-			local, domain, err := ParseEmailAddress(recip)
+			local, domain, err := stringutil.ParseEmailAddress(recip)
 			if err != nil {
 				ss.logError("Failed to parse address for %q", recip)
 				ss.send(fmt.Sprintf("451 Failed to open mailbox for %v", recip))
@@ -510,20 +512,16 @@ func (ss *Session) send(msg string) {
 
 // readByteLine reads a line of input into the provided buffer. Does
 // not reset the Buffer - please do so prior to calling.
-func (ss *Session) readByteLine(buf *bytes.Buffer) error {
+func (ss *Session) readByteLine(buf io.Writer) error {
 	if err := ss.conn.SetReadDeadline(ss.nextDeadline()); err != nil {
 		return err
 	}
-	for {
-		line, err := ss.reader.ReadBytes('\n')
-		if err != nil {
-			return err
-		}
-		if _, err = buf.Write(line); err != nil {
-			return err
-		}
-		return nil
+	line, err := ss.reader.ReadBytes('\n')
+	if err != nil {
+		return err
 	}
+	_, err = buf.Write(line)
+	return err
 }
 
 // Reads a line of input
@@ -572,7 +570,7 @@ func (ss *Session) parseCmd(line string) (cmd string, arg string, ok bool) {
 // The leading space is mandatory.
 func (ss *Session) parseArgs(arg string) (args map[string]string, ok bool) {
 	args = make(map[string]string)
-	re := regexp.MustCompile(" (\\w+)=(\\w+)")
+	re := regexp.MustCompile(` (\w+)=(\w+)`)
 	pm := re.FindAllStringSubmatch(arg, -1)
 	if pm == nil {
 		ss.logWarn("Failed to parse arg string: %q")
diff --git a/smtpd/handler_test.go b/smtpd/handler_test.go
index 61d4f69..e541f4e 100644
--- a/smtpd/handler_test.go
+++ b/smtpd/handler_test.go
@@ -14,6 +14,7 @@ import (
 	"time"
 
 	"github.com/jhillyerd/inbucket/config"
+	"github.com/jhillyerd/inbucket/datastore"
 	"github.com/jhillyerd/inbucket/msghub"
 )
 
@@ -25,17 +26,13 @@ type scriptStep struct {
 // Test commands in GREET state
 func TestGreetState(t *testing.T) {
 	// Setup mock objects
-	mds := &MockDataStore{}
-	mb1 := &MockMailbox{}
-	mds.On("MailboxFor").Return(mb1, nil)
+	mds := &datastore.MockDataStore{}
 
 	server, logbuf, teardown := setupSMTPServer(mds)
 	defer teardown()
 
-	var script []scriptStep
-
 	// Test out some mangled HELOs
-	script = []scriptStep{
+	script := []scriptStep{
 		{"HELO", 501},
 		{"EHLO", 501},
 		{"HELLO", 500},
@@ -86,17 +83,13 @@ func TestGreetState(t *testing.T) {
 // Test commands in READY state
 func TestReadyState(t *testing.T) {
 	// Setup mock objects
-	mds := &MockDataStore{}
-	mb1 := &MockMailbox{}
-	mds.On("MailboxFor").Return(mb1, nil)
+	mds := &datastore.MockDataStore{}
 
 	server, logbuf, teardown := setupSMTPServer(mds)
 	defer teardown()
 
-	var script []scriptStep
-
 	// Test out some mangled READY commands
-	script = []scriptStep{
+	script := []scriptStep{
 		{"HELO localhost", 250},
 		{"FOOB", 500},
 		{"HELO", 503},
@@ -151,10 +144,10 @@ func TestReadyState(t *testing.T) {
 // Test commands in MAIL state
 func TestMailState(t *testing.T) {
 	// Setup mock objects
-	mds := &MockDataStore{}
-	mb1 := &MockMailbox{}
-	msg1 := &MockMessage{}
-	mds.On("MailboxFor").Return(mb1, nil)
+	mds := &datastore.MockDataStore{}
+	mb1 := &datastore.MockMailbox{}
+	msg1 := &datastore.MockMessage{}
+	mds.On("MailboxFor", "u1").Return(mb1, nil)
 	mb1.On("NewMessage").Return(msg1, nil)
 	mb1.On("Name").Return("u1")
 	msg1.On("ID").Return("")
@@ -168,10 +161,8 @@ func TestMailState(t *testing.T) {
 	server, logbuf, teardown := setupSMTPServer(mds)
 	defer teardown()
 
-	var script []scriptStep
-
 	// Test out some mangled READY commands
-	script = []scriptStep{
+	script := []scriptStep{
 		{"HELO localhost", 250},
 		{"MAIL FROM:<john@gmail.com>", 250},
 		{"FOOB", 500},
@@ -268,10 +259,10 @@ func TestMailState(t *testing.T) {
 // Test commands in DATA state
 func TestDataState(t *testing.T) {
 	// Setup mock objects
-	mds := &MockDataStore{}
-	mb1 := &MockMailbox{}
-	msg1 := &MockMessage{}
-	mds.On("MailboxFor").Return(mb1, nil)
+	mds := &datastore.MockDataStore{}
+	mb1 := &datastore.MockMailbox{}
+	msg1 := &datastore.MockMessage{}
+	mds.On("MailboxFor", "u1").Return(mb1, nil)
 	mb1.On("NewMessage").Return(msg1, nil)
 	mb1.On("Name").Return("u1")
 	msg1.On("ID").Return("")
@@ -376,7 +367,7 @@ func (m *mockConn) SetDeadline(t time.Time) error      { return nil }
 func (m *mockConn) SetReadDeadline(t time.Time) error  { return nil }
 func (m *mockConn) SetWriteDeadline(t time.Time) error { return nil }
 
-func setupSMTPServer(ds DataStore) (s *Server, buf *bytes.Buffer, teardown func()) {
+func setupSMTPServer(ds datastore.DataStore) (s *Server, buf *bytes.Buffer, teardown func()) {
 	// Test Server Config
 	cfg := config.SMTPConfig{
 		IP4address:      net.IPv4(127, 0, 0, 1),
diff --git a/smtpd/listener.go b/smtpd/listener.go
index 11c4632..60953b6 100644
--- a/smtpd/listener.go
+++ b/smtpd/listener.go
@@ -11,10 +11,31 @@ import (
 	"time"
 
 	"github.com/jhillyerd/inbucket/config"
+	"github.com/jhillyerd/inbucket/datastore"
 	"github.com/jhillyerd/inbucket/log"
 	"github.com/jhillyerd/inbucket/msghub"
 )
 
+func init() {
+	m := expvar.NewMap("smtp")
+	m.Set("ConnectsTotal", expConnectsTotal)
+	m.Set("ConnectsHist", expConnectsHist)
+	m.Set("ConnectsCurrent", expConnectsCurrent)
+	m.Set("ReceivedTotal", expReceivedTotal)
+	m.Set("ReceivedHist", expReceivedHist)
+	m.Set("ErrorsTotal", expErrorsTotal)
+	m.Set("ErrorsHist", expErrorsHist)
+	m.Set("WarnsTotal", expWarnsTotal)
+	m.Set("WarnsHist", expWarnsHist)
+
+	log.AddTickerFunc(func() {
+		expReceivedHist.Set(log.PushMetric(deliveredHist, expReceivedTotal))
+		expConnectsHist.Set(log.PushMetric(connectsHist, expConnectsTotal))
+		expErrorsHist.Set(log.PushMetric(errorsHist, expErrorsTotal))
+		expWarnsHist.Set(log.PushMetric(warnsHist, expWarnsTotal))
+	})
+}
+
 // Server holds the configuration and state of our SMTP server
 type Server struct {
 	// Configuration
@@ -27,10 +48,10 @@ type Server struct {
 	storeMessages   bool
 
 	// Dependencies
-	dataStore        DataStore         // Mailbox/message store
-	globalShutdown   chan bool         // Shuts down Inbucket
-	msgHub           *msghub.Hub       // Pub/sub for message info
-	retentionScanner *RetentionScanner // Deletes expired messages
+	dataStore        datastore.DataStore         // Mailbox/message store
+	globalShutdown   chan bool                   // Shuts down Inbucket
+	msgHub           *msghub.Hub                 // Pub/sub for message info
+	retentionScanner *datastore.RetentionScanner // Deletes expired messages
 
 	// State
 	listener  net.Listener    // Incoming network connections
@@ -62,7 +83,7 @@ var (
 func NewServer(
 	cfg config.SMTPConfig,
 	globalShutdown chan bool,
-	ds DataStore,
+	ds datastore.DataStore,
 	msgHub *msghub.Hub) *Server {
 	return &Server{
 		host:             fmt.Sprintf("%v:%v", cfg.IP4address, cfg.IP4port),
@@ -75,7 +96,7 @@ func NewServer(
 		globalShutdown:   globalShutdown,
 		dataStore:        ds,
 		msgHub:           msgHub,
-		retentionScanner: NewRetentionScanner(ds, globalShutdown),
+		retentionScanner: datastore.NewRetentionScanner(ds, globalShutdown),
 		waitgroup:        new(sync.WaitGroup),
 	}
 }
@@ -110,10 +131,8 @@ func (s *Server) Start(ctx context.Context) {
 	go s.serve(ctx)
 
 	// Wait for shutdown
-	select {
-	case <-ctx.Done():
-		log.Tracef("SMTP shutdown requested, connections will be drained")
-	}
+	<-ctx.Done()
+	log.Tracef("SMTP shutdown requested, connections will be drained")
 
 	// Closing the listener will cause the serve() go routine to exit
 	if err := s.listener.Close(); err != nil {
@@ -165,7 +184,7 @@ func (s *Server) serve(ctx context.Context) {
 func (s *Server) emergencyShutdown() {
 	// Shutdown Inbucket
 	select {
-	case _ = <-s.globalShutdown:
+	case <-s.globalShutdown:
 	default:
 		close(s.globalShutdown)
 	}
@@ -178,44 +197,3 @@ func (s *Server) Drain() {
 	log.Tracef("SMTP connections have drained")
 	s.retentionScanner.Join()
 }
-
-// When the provided Ticker ticks, we update our metrics history
-func metricsTicker(t *time.Ticker) {
-	ok := true
-	for ok {
-		_, ok = <-t.C
-		expReceivedHist.Set(pushMetric(deliveredHist, expReceivedTotal))
-		expConnectsHist.Set(pushMetric(connectsHist, expConnectsTotal))
-		expErrorsHist.Set(pushMetric(errorsHist, expErrorsTotal))
-		expWarnsHist.Set(pushMetric(warnsHist, expWarnsTotal))
-		expRetentionDeletesHist.Set(pushMetric(retentionDeletesHist, expRetentionDeletesTotal))
-		expRetainedHist.Set(pushMetric(retainedHist, expRetainedCurrent))
-	}
-}
-
-// pushMetric adds the metric to the end of the list and returns a comma separated string of the
-// previous 61 entries.  We return 61 instead of 60 (an hour) because the chart on the client
-// tracks deltas between these values - there is nothing to compare the first value against.
-func pushMetric(history *list.List, ev expvar.Var) string {
-	history.PushBack(ev.String())
-	if history.Len() > 61 {
-		history.Remove(history.Front())
-	}
-	return JoinStringList(history)
-}
-
-func init() {
-	m := expvar.NewMap("smtp")
-	m.Set("ConnectsTotal", expConnectsTotal)
-	m.Set("ConnectsHist", expConnectsHist)
-	m.Set("ConnectsCurrent", expConnectsCurrent)
-	m.Set("ReceivedTotal", expReceivedTotal)
-	m.Set("ReceivedHist", expReceivedHist)
-	m.Set("ErrorsTotal", expErrorsTotal)
-	m.Set("ErrorsHist", expErrorsHist)
-	m.Set("WarnsTotal", expWarnsTotal)
-	m.Set("WarnsHist", expWarnsHist)
-
-	t := time.NewTicker(time.Minute)
-	go metricsTicker(t)
-}
diff --git a/smtpd/retention_test.go b/smtpd/retention_test.go
deleted file mode 100644
index 5e76b42..0000000
--- a/smtpd/retention_test.go
+++ /dev/null
@@ -1,197 +0,0 @@
-package smtpd
-
-import (
-	"fmt"
-	"io"
-	"net/mail"
-	"testing"
-	"time"
-
-	"github.com/jhillyerd/enmime"
-	"github.com/stretchr/testify/mock"
-)
-
-func TestDoRetentionScan(t *testing.T) {
-	// Create mock objects
-	mds := &MockDataStore{}
-
-	mb1 := &MockMailbox{}
-	mb2 := &MockMailbox{}
-	mb3 := &MockMailbox{}
-
-	// Mockup some different aged messages (num is in hours)
-	new1 := mockMessage(0)
-	new2 := mockMessage(1)
-	new3 := mockMessage(2)
-	old1 := mockMessage(4)
-	old2 := mockMessage(12)
-	old3 := mockMessage(24)
-
-	// First it should ask for all mailboxes
-	mds.On("AllMailboxes").Return([]Mailbox{mb1, mb2, mb3}, nil)
-
-	// Then for all messages on each box
-	mb1.On("GetMessages").Return([]Message{new1, old1, old2}, nil)
-	mb2.On("GetMessages").Return([]Message{old3, new2}, nil)
-	mb3.On("GetMessages").Return([]Message{new3}, nil)
-
-	// Test 4 hour retention
-	rs := &RetentionScanner{
-		ds:              mds,
-		retentionPeriod: 4*time.Hour - time.Minute,
-		retentionSleep:  0,
-	}
-	if err := rs.doScan(); err != nil {
-		t.Error(err)
-	}
-
-	// Check our assertions
-	mds.AssertExpectations(t)
-	mb1.AssertExpectations(t)
-	mb2.AssertExpectations(t)
-	mb3.AssertExpectations(t)
-
-	// Delete should not have been called on new messages
-	new1.AssertNotCalled(t, "Delete")
-	new2.AssertNotCalled(t, "Delete")
-	new3.AssertNotCalled(t, "Delete")
-
-	// Delete should have been called once on old messages
-	old1.AssertNumberOfCalls(t, "Delete", 1)
-	old2.AssertNumberOfCalls(t, "Delete", 1)
-	old3.AssertNumberOfCalls(t, "Delete", 1)
-}
-
-// Make a MockMessage of a specific age
-func mockMessage(ageHours int) *MockMessage {
-	msg := &MockMessage{}
-	msg.On("ID").Return(fmt.Sprintf("MSG[age=%vh]", ageHours))
-	msg.On("Date").Return(time.Now().Add(time.Duration(ageHours*-1) * time.Hour))
-	msg.On("Delete").Return(nil)
-	return msg
-}
-
-// Mock DataStore object
-type MockDataStore struct {
-	mock.Mock
-}
-
-func (m *MockDataStore) MailboxFor(name string) (Mailbox, error) {
-	args := m.Called()
-	return args.Get(0).(Mailbox), args.Error(1)
-}
-
-func (m *MockDataStore) AllMailboxes() ([]Mailbox, error) {
-	args := m.Called()
-	return args.Get(0).([]Mailbox), args.Error(1)
-}
-
-// Mock Mailbox object
-type MockMailbox struct {
-	mock.Mock
-}
-
-func (m *MockMailbox) GetMessages() ([]Message, error) {
-	args := m.Called()
-	return args.Get(0).([]Message), args.Error(1)
-}
-
-func (m *MockMailbox) GetMessage(id string) (Message, error) {
-	args := m.Called(id)
-	return args.Get(0).(Message), args.Error(1)
-}
-
-func (m *MockMailbox) Purge() error {
-	args := m.Called()
-	return args.Error(0)
-}
-
-func (m *MockMailbox) NewMessage() (Message, error) {
-	args := m.Called()
-	return args.Get(0).(Message), args.Error(1)
-}
-
-func (m *MockMailbox) Name() string {
-	args := m.Called()
-	return args.String(0)
-}
-
-func (m *MockMailbox) String() string {
-	args := m.Called()
-	return args.String(0)
-}
-
-// Mock Message object
-type MockMessage struct {
-	mock.Mock
-}
-
-func (m *MockMessage) ID() string {
-	args := m.Called()
-	return args.String(0)
-}
-
-func (m *MockMessage) From() string {
-	args := m.Called()
-	return args.String(0)
-}
-
-func (m *MockMessage) To() []string {
-	args := m.Called()
-	return args.Get(0).([]string)
-}
-
-func (m *MockMessage) Date() time.Time {
-	args := m.Called()
-	return args.Get(0).(time.Time)
-}
-
-func (m *MockMessage) Subject() string {
-	args := m.Called()
-	return args.String(0)
-}
-
-func (m *MockMessage) ReadHeader() (msg *mail.Message, err error) {
-	args := m.Called()
-	return args.Get(0).(*mail.Message), args.Error(1)
-}
-
-func (m *MockMessage) ReadBody() (body *enmime.Envelope, err error) {
-	args := m.Called()
-	return args.Get(0).(*enmime.Envelope), args.Error(1)
-}
-
-func (m *MockMessage) ReadRaw() (raw *string, err error) {
-	args := m.Called()
-	return args.Get(0).(*string), args.Error(1)
-}
-
-func (m *MockMessage) RawReader() (reader io.ReadCloser, err error) {
-	args := m.Called()
-	return args.Get(0).(io.ReadCloser), args.Error(1)
-}
-
-func (m *MockMessage) Size() int64 {
-	args := m.Called()
-	return int64(args.Int(0))
-}
-
-func (m *MockMessage) Append(data []byte) error {
-	// []byte arg seems to mess up testify/mock
-	return nil
-}
-
-func (m *MockMessage) Close() error {
-	args := m.Called()
-	return args.Error(0)
-}
-
-func (m *MockMessage) Delete() error {
-	args := m.Called()
-	return args.Error(0)
-}
-
-func (m *MockMessage) String() string {
-	args := m.Called()
-	return args.String(0)
-}
diff --git a/smtpd/utils.go b/stringutil/utils.go
similarity index 88%
rename from smtpd/utils.go
rename to stringutil/utils.go
index a8dcfb7..450ae1f 100644
--- a/smtpd/utils.go
+++ b/stringutil/utils.go
@@ -1,8 +1,7 @@
-package smtpd
+package stringutil
 
 import (
 	"bytes"
-	"container/list"
 	"crypto/sha1"
 	"fmt"
 	"io"
@@ -42,7 +41,7 @@ func ParseMailboxName(localPart string) (result string, err error) {
 	return result, nil
 }
 
-// HashMailboxName accepts a mailbox name and hashes it.  Inbucket uses this as
+// HashMailboxName accepts a mailbox name and hashes it.  filestore uses this as
 // the directory to house the mailbox
 func HashMailboxName(mailbox string) string {
 	h := sha1.New()
@@ -53,18 +52,6 @@ func HashMailboxName(mailbox string) string {
 	return fmt.Sprintf("%x", h.Sum(nil))
 }
 
-// JoinStringList joins a List containing strings by commas
-func JoinStringList(listOfStrings *list.List) string {
-	if listOfStrings.Len() == 0 {
-		return ""
-	}
-	s := make([]string, 0, listOfStrings.Len())
-	for e := listOfStrings.Front(); e != nil; e = e.Next() {
-		s = append(s, e.Value.(string))
-	}
-	return strings.Join(s, ",")
-}
-
 // ValidateDomainPart returns true if the domain part complies to RFC3696, RFC1035
 func ValidateDomainPart(domain string) bool {
 	if len(domain) == 0 {
@@ -143,15 +130,24 @@ LOOP:
 		switch {
 		case ('a' <= c && c <= 'z') || ('A' <= c && c <= 'Z'):
 			// Letters are OK
-			_ = buf.WriteByte(c)
+			err = buf.WriteByte(c)
+			if err != nil {
+				return
+			}
 			inCharQuote = false
 		case '0' <= c && c <= '9':
 			// Numbers are OK
-			_ = buf.WriteByte(c)
+			err = buf.WriteByte(c)
+			if err != nil {
+				return
+			}
 			inCharQuote = false
 		case bytes.IndexByte([]byte("!#$%&'*+-/=?^_`{|}~"), c) >= 0:
 			// These specials can be used unquoted
-			_ = buf.WriteByte(c)
+			err = buf.WriteByte(c)
+			if err != nil {
+				return
+			}
 			inCharQuote = false
 		case c == '.':
 			// A single period is OK
@@ -159,13 +155,19 @@ LOOP:
 				// Sequence of periods is not permitted
 				return "", "", fmt.Errorf("Sequence of periods is not permitted")
 			}
-			_ = buf.WriteByte(c)
+			err = buf.WriteByte(c)
+			if err != nil {
+				return
+			}
 			inCharQuote = false
 		case c == '\\':
 			inCharQuote = true
 		case c == '"':
 			if inCharQuote {
-				_ = buf.WriteByte(c)
+				err = buf.WriteByte(c)
+				if err != nil {
+					return
+				}
 				inCharQuote = false
 			} else if inStringQuote {
 				inStringQuote = false
@@ -178,7 +180,10 @@ LOOP:
 			}
 		case c == '@':
 			if inCharQuote || inStringQuote {
-				_ = buf.WriteByte(c)
+				err = buf.WriteByte(c)
+				if err != nil {
+					return
+				}
 				inCharQuote = false
 			} else {
 				// End of local-part
@@ -195,7 +200,10 @@ LOOP:
 			return "", "", fmt.Errorf("Characters outside of US-ASCII range not permitted")
 		default:
 			if inCharQuote || inStringQuote {
-				_ = buf.WriteByte(c)
+				err = buf.WriteByte(c)
+				if err != nil {
+					return
+				}
 				inCharQuote = false
 			} else {
 				return "", "", fmt.Errorf("Character %q must be quoted", c)
diff --git a/smtpd/utils_test.go b/stringutil/utils_test.go
similarity index 99%
rename from smtpd/utils_test.go
rename to stringutil/utils_test.go
index ae4fda3..330bfbd 100644
--- a/smtpd/utils_test.go
+++ b/stringutil/utils_test.go
@@ -1,4 +1,4 @@
-package smtpd
+package stringutil
 
 import (
 	"strings"
diff --git a/webui/mailbox_controller.go b/webui/mailbox_controller.go
index 35126db..b7c8a4e 100644
--- a/webui/mailbox_controller.go
+++ b/webui/mailbox_controller.go
@@ -7,9 +7,10 @@ import (
 	"net/http"
 	"strconv"
 
+	"github.com/jhillyerd/inbucket/datastore"
 	"github.com/jhillyerd/inbucket/httpd"
 	"github.com/jhillyerd/inbucket/log"
-	"github.com/jhillyerd/inbucket/smtpd"
+	"github.com/jhillyerd/inbucket/stringutil"
 )
 
 // MailboxIndex renders the index page for a particular mailbox
@@ -23,7 +24,7 @@ func MailboxIndex(w http.ResponseWriter, req *http.Request, ctx *httpd.Context)
 		http.Redirect(w, req, httpd.Reverse("RootIndex"), http.StatusSeeOther)
 		return nil
 	}
-	name, err = smtpd.ParseMailboxName(name)
+	name, err = stringutil.ParseMailboxName(name)
 	if err != nil {
 		ctx.Session.AddFlash(err.Error(), "errors")
 		_ = ctx.Session.Save(req, w)
@@ -50,7 +51,7 @@ func MailboxIndex(w http.ResponseWriter, req *http.Request, ctx *httpd.Context)
 func MailboxLink(w http.ResponseWriter, req *http.Request, ctx *httpd.Context) (err error) {
 	// Don't have to validate these aren't empty, Gorilla returns 404
 	id := ctx.Vars["id"]
-	name, err := smtpd.ParseMailboxName(ctx.Vars["name"])
+	name, err := stringutil.ParseMailboxName(ctx.Vars["name"])
 	if err != nil {
 		ctx.Session.AddFlash(err.Error(), "errors")
 		_ = ctx.Session.Save(req, w)
@@ -66,7 +67,7 @@ func MailboxLink(w http.ResponseWriter, req *http.Request, ctx *httpd.Context) (
 // MailboxList renders a list of messages in a mailbox. Renders a partial
 func MailboxList(w http.ResponseWriter, req *http.Request, ctx *httpd.Context) (err error) {
 	// Don't have to validate these aren't empty, Gorilla returns 404
-	name, err := smtpd.ParseMailboxName(ctx.Vars["name"])
+	name, err := stringutil.ParseMailboxName(ctx.Vars["name"])
 	if err != nil {
 		return err
 	}
@@ -93,7 +94,7 @@ func MailboxList(w http.ResponseWriter, req *http.Request, ctx *httpd.Context) (
 func MailboxShow(w http.ResponseWriter, req *http.Request, ctx *httpd.Context) (err error) {
 	// Don't have to validate these aren't empty, Gorilla returns 404
 	id := ctx.Vars["id"]
-	name, err := smtpd.ParseMailboxName(ctx.Vars["name"])
+	name, err := stringutil.ParseMailboxName(ctx.Vars["name"])
 	if err != nil {
 		return err
 	}
@@ -103,7 +104,7 @@ func MailboxShow(w http.ResponseWriter, req *http.Request, ctx *httpd.Context) (
 		return fmt.Errorf("Failed to get mailbox for %q: %v", name, err)
 	}
 	msg, err := mb.GetMessage(id)
-	if err == smtpd.ErrNotExist {
+	if err == datastore.ErrNotExist {
 		http.NotFound(w, req)
 		return nil
 	}
@@ -133,7 +134,7 @@ func MailboxShow(w http.ResponseWriter, req *http.Request, ctx *httpd.Context) (
 func MailboxHTML(w http.ResponseWriter, req *http.Request, ctx *httpd.Context) (err error) {
 	// Don't have to validate these aren't empty, Gorilla returns 404
 	id := ctx.Vars["id"]
-	name, err := smtpd.ParseMailboxName(ctx.Vars["name"])
+	name, err := stringutil.ParseMailboxName(ctx.Vars["name"])
 	if err != nil {
 		return err
 	}
@@ -143,7 +144,7 @@ func MailboxHTML(w http.ResponseWriter, req *http.Request, ctx *httpd.Context) (
 		return fmt.Errorf("Failed to get mailbox for %q: %v", name, err)
 	}
 	message, err := mb.GetMessage(id)
-	if err == smtpd.ErrNotExist {
+	if err == datastore.ErrNotExist {
 		http.NotFound(w, req)
 		return nil
 	}
@@ -170,7 +171,7 @@ func MailboxHTML(w http.ResponseWriter, req *http.Request, ctx *httpd.Context) (
 func MailboxSource(w http.ResponseWriter, req *http.Request, ctx *httpd.Context) (err error) {
 	// Don't have to validate these aren't empty, Gorilla returns 404
 	id := ctx.Vars["id"]
-	name, err := smtpd.ParseMailboxName(ctx.Vars["name"])
+	name, err := stringutil.ParseMailboxName(ctx.Vars["name"])
 	if err != nil {
 		return err
 	}
@@ -180,7 +181,7 @@ func MailboxSource(w http.ResponseWriter, req *http.Request, ctx *httpd.Context)
 		return fmt.Errorf("Failed to get mailbox for %q: %v", name, err)
 	}
 	message, err := mb.GetMessage(id)
-	if err == smtpd.ErrNotExist {
+	if err == datastore.ErrNotExist {
 		http.NotFound(w, req)
 		return nil
 	}
@@ -205,7 +206,7 @@ func MailboxSource(w http.ResponseWriter, req *http.Request, ctx *httpd.Context)
 func MailboxDownloadAttach(w http.ResponseWriter, req *http.Request, ctx *httpd.Context) (err error) {
 	// Don't have to validate these aren't empty, Gorilla returns 404
 	id := ctx.Vars["id"]
-	name, err := smtpd.ParseMailboxName(ctx.Vars["name"])
+	name, err := stringutil.ParseMailboxName(ctx.Vars["name"])
 	if err != nil {
 		ctx.Session.AddFlash(err.Error(), "errors")
 		_ = ctx.Session.Save(req, w)
@@ -226,7 +227,7 @@ func MailboxDownloadAttach(w http.ResponseWriter, req *http.Request, ctx *httpd.
 		return fmt.Errorf("Failed to get mailbox for %q: %v", name, err)
 	}
 	message, err := mb.GetMessage(id)
-	if err == smtpd.ErrNotExist {
+	if err == datastore.ErrNotExist {
 		http.NotFound(w, req)
 		return nil
 	}
@@ -257,7 +258,7 @@ func MailboxDownloadAttach(w http.ResponseWriter, req *http.Request, ctx *httpd.
 // MailboxViewAttach sends the attachment to the client for online viewing
 func MailboxViewAttach(w http.ResponseWriter, req *http.Request, ctx *httpd.Context) (err error) {
 	// Don't have to validate these aren't empty, Gorilla returns 404
-	name, err := smtpd.ParseMailboxName(ctx.Vars["name"])
+	name, err := stringutil.ParseMailboxName(ctx.Vars["name"])
 	if err != nil {
 		ctx.Session.AddFlash(err.Error(), "errors")
 		_ = ctx.Session.Save(req, w)
@@ -279,7 +280,7 @@ func MailboxViewAttach(w http.ResponseWriter, req *http.Request, ctx *httpd.Cont
 		return fmt.Errorf("Failed to get mailbox for %q: %v", name, err)
 	}
 	message, err := mb.GetMessage(id)
-	if err == smtpd.ErrNotExist {
+	if err == datastore.ErrNotExist {
 		http.NotFound(w, req)
 		return nil
 	}
diff --git a/webui/root_controller.go b/webui/root_controller.go
index 651e686..9a64bc5 100644
--- a/webui/root_controller.go
+++ b/webui/root_controller.go
@@ -8,7 +8,7 @@ import (
 
 	"github.com/jhillyerd/inbucket/config"
 	"github.com/jhillyerd/inbucket/httpd"
-	"github.com/jhillyerd/inbucket/smtpd"
+	"github.com/jhillyerd/inbucket/stringutil"
 )
 
 // RootIndex serves the Inbucket landing page
@@ -58,7 +58,7 @@ func RootMonitorMailbox(w http.ResponseWriter, req *http.Request, ctx *httpd.Con
 		http.Redirect(w, req, httpd.Reverse("RootIndex"), http.StatusSeeOther)
 		return nil
 	}
-	name, err := smtpd.ParseMailboxName(ctx.Vars["name"])
+	name, err := stringutil.ParseMailboxName(ctx.Vars["name"])
 	if err != nil {
 		ctx.Session.AddFlash(err.Error(), "errors")
 		_ = ctx.Session.Save(req, w)