Index: Lib/email/message.py
===================================================================
--- Lib/email/message.py	(revision 80676)
+++ Lib/email/message.py	(working copy)
@@ -384,6 +384,11 @@
             if k.lower() == name:
                 values.append(v)
         if not values:
+            if failobj and not isinstance(failobj, list):
+                if isinstance(failobj, str):
+                    failobj = [failobj]
+                else:
+                    failobj = list(failobj)
             return failobj
         return values