diff --git a/const.go b/const.go
index 98164a8..07beaa3 100644
--- a/const.go
+++ b/const.go
@@ -10,4 +10,11 @@ const (
 	FileNameUserForwards  = ".forward"
 	FileNameAliasUsers    = ".valiases"
 	FileNameCatchAllUser  = ".vcatchall"
+
+	FileNameDbDomains      = "domains"
+	FileNameDbDestinations = "destinations"
+	FileNameDbMaildirs     = "maildirs"
+	FileNameDbLocaltable   = "localtable"
+	FileNameDbForwards     = "forwards"
+	FileNameDbPasswords    = "vpasswd"
 )
diff --git a/database.go b/database.go
new file mode 100644
index 0000000..f9b684c
--- /dev/null
+++ b/database.go
@@ -0,0 +1,201 @@
+package mailfull
+
+import (
+	"fmt"
+	"os"
+	"os/exec"
+	"path/filepath"
+	"sort"
+	"strings"
+)
+
+// GenerateDatabases generates databases from the MailData directory.
+func (r *Repository) GenerateDatabases(md *MailData) error {
+	sort.Sort(DomainSlice(md.Domains))
+	sort.Sort(AliasDomainSlice(md.AliasDomains))
+
+	for _, domain := range md.Domains {
+		sort.Sort(UserSlice(domain.Users))
+		sort.Sort(AliasUserSlice(domain.AliasUsers))
+	}
+
+	// Generate files
+	if err := r.generateDbDomains(md); err != nil {
+		return err
+	}
+	if err := r.generateDbDestinations(md); err != nil {
+		return err
+	}
+	if err := r.generateDbMaildirs(md); err != nil {
+		return err
+	}
+	if err := r.generateDbLocaltable(md); err != nil {
+		return err
+	}
+	if err := r.generateDbForwards(md); err != nil {
+		return err
+	}
+	if err := r.generateDbPasswords(md); err != nil {
+		return err
+	}
+
+	// Generate DBs
+	if err := exec.Command(r.CmdPostmap, filepath.Join(r.DirDatabasePath, FileNameDbDomains)).Run(); err != nil {
+		return err
+	}
+	if err := exec.Command(r.CmdPostmap, filepath.Join(r.DirDatabasePath, FileNameDbDestinations)).Run(); err != nil {
+		return err
+	}
+	if err := exec.Command(r.CmdPostmap, filepath.Join(r.DirDatabasePath, FileNameDbMaildirs)).Run(); err != nil {
+		return err
+	}
+	if err := exec.Command(r.CmdPostmap, filepath.Join(r.DirDatabasePath, FileNameDbLocaltable)).Run(); err != nil {
+		return err
+	}
+	if err := exec.Command(r.CmdPostalias, filepath.Join(r.DirDatabasePath, FileNameDbForwards)).Run(); err != nil {
+		return err
+	}
+
+	return nil
+}
+
+func (r *Repository) generateDbDomains(md *MailData) error {
+	dbDomains, err := os.Create(filepath.Join(r.DirDatabasePath, FileNameDbDomains))
+	if err != nil {
+		return err
+	}
+	defer dbDomains.Close()
+
+	for _, domain := range md.Domains {
+		fmt.Fprintf(dbDomains, "%s virtual\n", domain.Name())
+	}
+
+	for _, aliasDomain := range md.AliasDomains {
+		fmt.Fprintf(dbDomains, "%s virtual\n", aliasDomain.Name())
+	}
+
+	return nil
+}
+
+func (r *Repository) generateDbDestinations(md *MailData) error {
+	dbDestinations, err := os.Create(filepath.Join(r.DirDatabasePath, FileNameDbDestinations))
+	if err != nil {
+		return err
+	}
+	defer dbDestinations.Close()
+
+	for _, domain := range md.Domains {
+		// ho-ge.example.com -> ho_ge.example.com
+		underscoredDomainName := domain.Name()
+		underscoredDomainName = strings.Replace(underscoredDomainName, `-`, `_`, -1)
+
+		for _, user := range domain.Users {
+			userName := user.Name()
+			if cu := domain.CatchAllUser; cu != nil && cu.Name() == user.Name() {
+				userName = ""
+			}
+
+			if len(user.Forwards()) > 0 {
+				fmt.Fprintf(dbDestinations, "%s@%s %s|%s\n", userName, domain.Name(), underscoredDomainName, user.Name())
+			} else {
+				fmt.Fprintf(dbDestinations, "%s@%s %s@%s\n", userName, domain.Name(), user.Name(), domain.Name())
+			}
+
+			for _, aliasDomain := range md.AliasDomains {
+				if aliasDomain.Target() == domain.Name() {
+					fmt.Fprintf(dbDestinations, "%s@%s %s@%s\n", userName, aliasDomain.Name(), user.Name(), domain.Name())
+				}
+			}
+		}
+
+		for _, aliasUser := range domain.AliasUsers {
+			fmt.Fprintf(dbDestinations, "%s@%s %s\n", aliasUser.Name(), domain.Name(), strings.Join(aliasUser.Targets(), ","))
+
+			for _, aliasDomain := range md.AliasDomains {
+				if aliasDomain.Target() == domain.Name() {
+					fmt.Fprintf(dbDestinations, "%s@%s %s@%s\n", aliasUser.Name(), aliasDomain.Name(), aliasUser.Name(), domain.Name())
+				}
+			}
+		}
+	}
+
+	return nil
+}
+
+func (r *Repository) generateDbMaildirs(md *MailData) error {
+	dbMaildirs, err := os.Create(filepath.Join(r.DirDatabasePath, FileNameDbMaildirs))
+	if err != nil {
+		return err
+	}
+	defer dbMaildirs.Close()
+
+	for _, domain := range md.Domains {
+		for _, user := range domain.Users {
+			fmt.Fprintf(dbMaildirs, "%s@%s %s/%s/Maildir/\n", user.Name(), domain.Name(), domain.Name(), user.Name())
+		}
+	}
+
+	return nil
+}
+
+func (r *Repository) generateDbLocaltable(md *MailData) error {
+	dbLocaltable, err := os.Create(filepath.Join(r.DirDatabasePath, FileNameDbLocaltable))
+	if err != nil {
+		return err
+	}
+	defer dbLocaltable.Close()
+
+	for _, domain := range md.Domains {
+		// ho-ge.example.com -> ho_ge\.example\.com
+		escapedDomainName := domain.Name()
+		escapedDomainName = strings.Replace(escapedDomainName, `-`, `_`, -1)
+		escapedDomainName = strings.Replace(escapedDomainName, `.`, `\.`, -1)
+
+		fmt.Fprintf(dbLocaltable, "/^%s\\|.*$/ local\n", escapedDomainName)
+	}
+
+	return nil
+}
+
+func (r *Repository) generateDbForwards(md *MailData) error {
+	dbForwards, err := os.Create(filepath.Join(r.DirDatabasePath, FileNameDbForwards))
+	if err != nil {
+		return err
+	}
+	defer dbForwards.Close()
+
+	for _, domain := range md.Domains {
+		// ho-ge.example.com -> ho_ge.example.com
+		underscoredDomainName := domain.Name()
+		underscoredDomainName = strings.Replace(underscoredDomainName, `-`, `_`, -1)
+
+		for _, user := range domain.Users {
+			if len(user.Forwards()) > 0 {
+				fmt.Fprintf(dbForwards, "%s|%s:%s\n", underscoredDomainName, user.Name(), strings.Join(user.Forwards(), ","))
+			} else {
+				fmt.Fprintf(dbForwards, "%s|%s:/dev/null\n", underscoredDomainName, user.Name())
+			}
+		}
+	}
+
+	// drop real user
+	fmt.Fprintf(dbForwards, "%s:/dev/null\n", r.Username)
+
+	return nil
+}
+
+func (r *Repository) generateDbPasswords(md *MailData) error {
+	dbPasswords, err := os.Create(filepath.Join(r.DirDatabasePath, FileNameDbPasswords))
+	if err != nil {
+		return err
+	}
+	defer dbPasswords.Close()
+
+	for _, domain := range md.Domains {
+		for _, user := range domain.Users {
+			fmt.Fprintf(dbPasswords, "%s@%s:%s\n", user.Name(), domain.Name(), user.HashedPassword())
+		}
+	}
+
+	return nil
+}
diff --git a/maildata.go b/maildata.go
new file mode 100644
index 0000000..7e32b38
--- /dev/null
+++ b/maildata.go
@@ -0,0 +1,47 @@
+package mailfull
+
+// MailData represents a MailData.
+type MailData struct {
+	Domains      []*Domain
+	AliasDomains []*AliasDomain
+}
+
+// MailData returns a MailData.
+func (r *Repository) MailData() (*MailData, error) {
+	domains, err := r.Domains()
+	if err != nil {
+		return nil, err
+	}
+
+	aliasDomains, err := r.AliasDomains()
+	if err != nil {
+		return nil, err
+	}
+
+	for _, domain := range domains {
+		users, err := r.Users(domain.Name())
+		if err != nil {
+			return nil, err
+		}
+		domain.Users = users
+
+		aliasUsers, err := r.AliasUsers(domain.Name())
+		if err != nil {
+			return nil, err
+		}
+		domain.AliasUsers = aliasUsers
+
+		catchAllUser, err := r.CatchAllUser(domain.Name())
+		if err != nil {
+			return nil, err
+		}
+		domain.CatchAllUser = catchAllUser
+	}
+
+	mailData := &MailData{
+		Domains:      domains,
+		AliasDomains: aliasDomains,
+	}
+
+	return mailData, nil
+}