diff --git a/security/manager/pki/resources/content/pippki.js b/security/manager/pki/resources/content/pippki.js
index cf967c1162b9..4d275e7f927b 100644
--- a/security/manager/pki/resources/content/pippki.js
+++ b/security/manager/pki/resources/content/pippki.js
@@ -31,7 +31,7 @@ async function viewCertHelper(parent, cert, openingOption = "tab") {
   }
 
   if (Services.prefs.getBoolPref("security.aboutcertificate.enabled")) {
-    let win = Services.wm.getMostRecentWindow("navigator:browser");
+    let win = Services.wm.getMostRecentBrowserWindow();
     let results = await asyncDetermineUsages(cert);
     let chain = getBestChain(results);
     if (!chain) {
diff --git a/xpfe/appshell/nsIWindowMediator.idl b/xpfe/appshell/nsIWindowMediator.idl
index cdf5a0dd6492..ef891c053717 100644
--- a/xpfe/appshell/nsIWindowMediator.idl
+++ b/xpfe/appshell/nsIWindowMediator.idl
@@ -67,7 +67,7 @@ interface nsIWindowMediator: nsISupports
   mozIDOMWindowProxy getMostRecentWindow(in wstring aWindowType);
 
   /** This is a shortcut for getMostRecentWindow('navigator:browser'), but
-    * it also tries 'navigator:geckoview' if that fails.
+    * if that fails it also tries 'navigator:geckoview' and 'mail:3pane'.
     *
     * @return the topmost browser window
     */
diff --git a/xpfe/appshell/nsWindowMediator.cpp b/xpfe/appshell/nsWindowMediator.cpp
index 1e59688c471f..ff2af1506345 100644
--- a/xpfe/appshell/nsWindowMediator.cpp
+++ b/xpfe/appshell/nsWindowMediator.cpp
@@ -245,6 +245,13 @@ nsWindowMediator::GetMostRecentBrowserWindow(mozIDOMWindowProxy** outWindow) {
   }
 #endif
 
+#ifdef MOZ_THUNDERBIRD
+  if (!*outWindow) {
+    rv = GetMostRecentWindow(u"mail:3pane", outWindow);
+    NS_ENSURE_SUCCESS(rv, rv);
+  }
+#endif
+
   return NS_OK;
 }