diff --git a/ui/src/Layout.elm b/ui/src/Layout.elm
index 3b0196f..e4ff701 100644
--- a/ui/src/Layout.elm
+++ b/ui/src/Layout.elm
@@ -38,7 +38,10 @@ import Html.Attributes
         )
 import Html.Events as Events
 import Modal
+import Process
 import Route exposing (Route)
+import Task
+import Timer exposing (Timer)
 
 
 {-| Used to highlight current page in navbar.
@@ -52,8 +55,9 @@ type Page
 
 type alias Model msg =
     { mapMsg : Msg -> msg
-    , menuVisible : Bool
-    , recentVisible : Bool
+    , mainMenuVisible : Bool
+    , recentMenuVisible : Bool
+    , recentMenuTimer : Timer
     , mailboxName : String
     }
 
@@ -61,8 +65,9 @@ type alias Model msg =
 init : (Msg -> msg) -> Model msg
 init mapMsg =
     { mapMsg = mapMsg
-    , menuVisible = False
-    , recentVisible = False
+    , mainMenuVisible = False
+    , recentMenuVisible = False
+    , recentMenuTimer = Timer.empty
     , mailboxName = ""
     }
 
@@ -72,20 +77,24 @@ init mapMsg =
 reset : Model msg -> Model msg
 reset model =
     { model
-        | menuVisible = False
-        , recentVisible = False
+        | mainMenuVisible = False
+        , recentMenuVisible = False
+        , recentMenuTimer = Timer.cancel model.recentMenuTimer
         , mailboxName = ""
     }
 
 
 type Msg
     = ClearFlash
+    | MainMenuToggled
     | ModalFocused Modal.Msg
     | ModalUnfocused
     | OnMailboxNameInput String
     | OpenMailbox
-    | ShowRecent Bool
-    | ToggleMenu
+    | RecentMenuMouseOver
+    | RecentMenuMouseOut
+    | RecentMenuTimeout Timer
+    | RecentMenuToggled
 
 
 update : Msg -> Model msg -> Session -> ( Model msg, Session, Cmd msg )
@@ -97,6 +106,12 @@ update msg model session =
             , Cmd.none
             )
 
+        MainMenuToggled ->
+            ( { model | mainMenuVisible = not model.mainMenuVisible }
+            , session
+            , Cmd.none
+            )
+
         ModalFocused message ->
             ( model
             , Modal.updateSession message session
@@ -122,14 +137,43 @@ update msg model session =
                 , Route.pushUrl session.key (Route.Mailbox model.mailboxName)
                 )
 
-        ShowRecent visible ->
-            ( { model | recentVisible = visible }
+        RecentMenuMouseOver ->
+            ( { model
+                | recentMenuVisible = True
+                , recentMenuTimer = Timer.cancel model.recentMenuTimer
+              }
             , session
             , Cmd.none
             )
 
-        ToggleMenu ->
-            ( { model | menuVisible = not model.menuVisible }
+        RecentMenuMouseOut ->
+            let
+                newTimer =
+                    Timer.replace model.recentMenuTimer
+            in
+            ( { model
+                | recentMenuTimer = newTimer
+              }
+            , session
+            , Timer.schedule (RecentMenuTimeout >> model.mapMsg) newTimer 400
+            )
+
+        RecentMenuTimeout timer ->
+            if timer == model.recentMenuTimer then
+                ( { model
+                    | recentMenuVisible = False
+                    , recentMenuTimer = Timer.cancel timer
+                  }
+                , session
+                , Cmd.none
+                )
+
+            else
+                -- Timer was no longer valid.
+                ( model, session, Cmd.none )
+
+        RecentMenuToggled ->
+            ( { model | recentMenuVisible = not model.recentMenuVisible }
             , session
             , Cmd.none
             )
@@ -150,11 +194,11 @@ frame { model, session, activePage, activeMailbox, modal, content } =
     div [ class "app" ]
         [ header []
             [ nav [ class "navbar" ]
-                [ button [ class "navbar-toggle", Events.onClick (ToggleMenu |> model.mapMsg) ]
+                [ button [ class "navbar-toggle", Events.onClick (MainMenuToggled |> model.mapMsg) ]
                     [ i [ class "fas fa-bars" ] [] ]
                 , span [ class "navbar-brand" ]
                     [ a [ Route.href Route.Home ] [ text "@ inbucket" ] ]
-                , ul [ class "main-nav", classList [ ( "active", model.menuVisible ) ] ]
+                , ul [ class "main-nav", classList [ ( "active", model.mainMenuVisible ) ] ]
                     [ if session.config.monitorVisible then
                         navbarLink Monitor Route.Monitor [ text "Monitor" ] activePage
 
@@ -256,15 +300,15 @@ navbarRecent page activeMailbox model session =
         [ class "navbar-dropdown-container"
         , classList [ ( "navbar-active", active ) ]
         , attribute "aria-haspopup" "true"
-        , ariaExpanded model.recentVisible
-        , Events.onMouseOver (ShowRecent True |> model.mapMsg)
-        , Events.onMouseOut (ShowRecent False |> model.mapMsg)
+        , ariaExpanded model.recentMenuVisible
+        , Events.onMouseOver (RecentMenuMouseOver |> model.mapMsg)
+        , Events.onMouseOut (RecentMenuMouseOut |> model.mapMsg)
         ]
         [ span [ class "navbar-dropdown" ]
             [ text title
             , button
                 [ class "navbar-dropdown-button"
-                , Events.onClick (ShowRecent (not model.recentVisible) |> model.mapMsg)
+                , Events.onClick (RecentMenuToggled |> model.mapMsg)
                 ]
                 [ i [ class "fas fa-chevron-down" ] [] ]
             ]
diff --git a/ui/src/Timer.elm b/ui/src/Timer.elm
new file mode 100644
index 0000000..fc82d44
--- /dev/null
+++ b/ui/src/Timer.elm
@@ -0,0 +1,58 @@
+module Timer exposing (Timer, cancel, empty, replace, schedule)
+
+import Process
+import Task
+
+
+{-| Implements an identity to track an asynchronous timer.
+-}
+type Timer
+    = Empty
+    | Idle Int
+    | Timer Int
+
+
+empty : Timer
+empty =
+    Empty
+
+
+schedule : (Timer -> msg) -> Timer -> Float -> Cmd msg
+schedule message timer millis =
+    Task.perform (always (message timer)) (Process.sleep millis)
+
+
+{-| Replaces the provided timer with a newly created one.
+-}
+replace : Timer -> Timer
+replace previous =
+    case previous of
+        Empty ->
+            Timer 0
+
+        Idle index ->
+            Timer (next index)
+
+        Timer index ->
+            Timer (next index)
+
+
+{-| Cancels the provided timer without creating a replacement.
+-}
+cancel : Timer -> Timer
+cancel previous =
+    case previous of
+        Timer index ->
+            Idle index
+
+        _ ->
+            previous
+
+
+next : Int -> Int
+next index =
+    if index > 2 ^ 30 then
+        0
+
+    else
+        index + 1