diff --git a/browser/installer/windows/nsis/shared.nsh b/browser/installer/windows/nsis/shared.nsh
--- a/browser/installer/windows/nsis/shared.nsh
+++ b/browser/installer/windows/nsis/shared.nsh
@@ -461,11 +461,10 @@
   ; protocol handlers already have a display name and the additional keys
   ; required for a protocol handler.
   ${AddDisabledDDEHandlerValues} "ftp" "$2" "$8,1" "" ""
   ${AddDisabledDDEHandlerValues} "http" "$2" "$8,1" "" ""
   ${AddDisabledDDEHandlerValues} "https" "$2" "$8,1" "" ""
-  ${AddDisabledDDEHandlerValues} "mailto" "$2" "$8,1" "" ""
 !macroend
 !define SetHandlers "!insertmacro SetHandlers"
 
 ; Adds the HKLM\Software\Clients\StartMenuInternet\Firefox-[pathhash] registry
 ; entries (does not use SHCTX).
@@ -537,11 +536,10 @@
   WriteRegStr ${RegKey} "$0\Capabilities\StartMenu" "StartMenuInternet" "$1"
 
   WriteRegStr ${RegKey} "$0\Capabilities\URLAssociations" "ftp"    "FirefoxURL$2"
   WriteRegStr ${RegKey} "$0\Capabilities\URLAssociations" "http"   "FirefoxURL$2"
   WriteRegStr ${RegKey} "$0\Capabilities\URLAssociations" "https"  "FirefoxURL$2"
-  WriteRegStr ${RegKey} "$0\Capabilities\URLAssociations" "mailto" "FirefoxURL$2"
 
   ; Registered Application
   WriteRegStr ${RegKey} "Software\RegisteredApplications" "$1" "$0\Capabilities"
 !macroend
 !define SetStartMenuInternet "!insertmacro SetStartMenuInternet"
@@ -884,15 +882,10 @@
 
   ${IsHandlerForInstallDir} "https" $R9
   ${If} "$R9" == "true"
     ${AddDisabledDDEHandlerValues} "https" "$2" "$8,1" "" ""
   ${EndIf}
-
-  ${IsHandlerForInstallDir} "mailto" $R9
-  ${If} "$R9" == "true"
-    ${AddDisabledDDEHandlerValues} "mailto" "$2" "$8,1" "" ""
-  ${EndIf}
 !macroend
 !define UpdateProtocolHandlers "!insertmacro UpdateProtocolHandlers"
 
 !ifdef MOZ_MAINTENANCE_SERVICE
 ; Adds maintenance service certificate keys for the install dir.
diff --git a/browser/installer/windows/nsis/uninstaller.nsi b/browser/installer/windows/nsis/uninstaller.nsi
--- a/browser/installer/windows/nsis/uninstaller.nsi
+++ b/browser/installer/windows/nsis/uninstaller.nsi
@@ -303,11 +303,10 @@
   ${un.RegCleanAppHandler} "FirefoxURL-$AppUserModelID"
   ${un.RegCleanAppHandler} "FirefoxHTML-$AppUserModelID"
   ${un.RegCleanProtocolHandler} "ftp"
   ${un.RegCleanProtocolHandler} "http"
   ${un.RegCleanProtocolHandler} "https"
-  ${un.RegCleanProtocolHandler} "mailto"
   ${un.RegCleanFileHandler}  ".htm"   "FirefoxHTML-$AppUserModelID"
   ${un.RegCleanFileHandler}  ".html"  "FirefoxHTML-$AppUserModelID"
   ${un.RegCleanFileHandler}  ".shtml" "FirefoxHTML-$AppUserModelID"
   ${un.RegCleanFileHandler}  ".xht"   "FirefoxHTML-$AppUserModelID"
   ${un.RegCleanFileHandler}  ".xhtml" "FirefoxHTML-$AppUserModelID"