diff --git a/mail/locales/en-US/chrome/communicator/utilityOverlay.dtd b/mail/locales/en-US/chrome/communicator/utilityOverlay.dtd
index e138afd0f8b..784fbb11bb1 100644
--- a/mail/locales/en-US/chrome/communicator/utilityOverlay.dtd
+++ b/mail/locales/en-US/chrome/communicator/utilityOverlay.dtd
@@ -62,6 +62,8 @@
 <!ENTITY closeCmd.key			"W">  
 <!ENTITY closeCmd.accesskey		"c">
 
+<!ENTITY closeWindow.label "Close Window">
+
 <!ENTITY quitApplicationCmd.label	"Exit"> 
 <!ENTITY quitApplicationCmd.key		"Q"> 
 <!ENTITY quitApplicationCmd.accesskey	"x">
diff --git a/mail/locales/en-US/chrome/messenger/messenger.dtd b/mail/locales/en-US/chrome/messenger/messenger.dtd
index 7072bdc875f..e36c7f0edca 100644
--- a/mail/locales/en-US/chrome/messenger/messenger.dtd
+++ b/mail/locales/en-US/chrome/messenger/messenger.dtd
@@ -5,6 +5,10 @@
 <!-- File Menu -->
 <!ENTITY newFolderCmd.label "Folder...">
 <!ENTITY newFolderCmd.accesskey "F">
+<!ENTITY newTabCmd.label "New Tab">
+<!ENTITY newTabCmd.accesskey "T">
+<!ENTITY newTabCmd.label "Close Tab">
+<!ENTITY newTabCmd.accesskey "e">
 <!ENTITY newVirtualFolderCmd.label "Saved Search...">
 <!ENTITY newVirtualFolderCmd.accesskey "S">
 <!ENTITY newAccountCmd.label "Account...">
@@ -491,6 +495,8 @@
 <!-- Folder Pane Context Menu -->
 <!ENTITY folderContextOpenNewWindow.label "Open">
 <!ENTITY folderContextOpenNewWindow.accesskey "O">
+<!ENTITY folderContextOpenNewTab.label "Open in New Tab">
+<!ENTITY folderContextOpenNewTab.accesskey "T">
 <!ENTITY folderContextNew.label "New Subfolder...">
 <!ENTITY folderContextNew.accesskey "N">
 <!ENTITY folderContextRename.label "Rename">
@@ -579,6 +585,8 @@
 <!-- Thread Pane Context Menu -->
 <!ENTITY contextOpenNewWindow.label "Open Message in New Window">
 <!ENTITY contextOpenNewWindow.accesskey "W">
+<!ENTITY contextOpenNewTab.label "Open Message in New Tab">
+<!ENTITY contextOpenNewTab.accesskey "T">
 <!ENTITY contextEditAsNew.label "Edit As New...">
 <!ENTITY contextEditAsNew.accesskey "E">
 <!ENTITY contextReplySender.label "Reply to Sender Only">
diff --git a/mail/locales/en-US/chrome/messenger/preferences/advanced.dtd b/mail/locales/en-US/chrome/messenger/preferences/advanced.dtd
index e5496c3b2e2..b2dad9fd5fa 100644
--- a/mail/locales/en-US/chrome/messenger/preferences/advanced.dtd
+++ b/mail/locales/en-US/chrome/messenger/preferences/advanced.dtd
@@ -24,6 +24,8 @@
 <!ENTITY reuseExpRadio0.accesskey      "i">
 <!ENTITY reuseExpRadio1.label          "An existing message window">
 <!ENTITY reuseExpRadio1.accesskey      "x">
+<!ENTITY reuseExpRadio2.label          "A new message tab">
+<!ENTITY reuseExpRadio2.accesskey      "Z">
 <!ENTITY connectionTimeout.label       "Connection timeout: ">
 <!ENTITY connectionTimeout.accesskey   "C">
 <!ENTITY connectionSeconds.label       "seconds">