#8989: add 'domain' keyword to make_msgid.

Patch by Adrian von Bidder.
diff --git a/Lib/email/test/test_email.py b/Lib/email/test/test_email.py
index 5545abe..7993486 100644
--- a/Lib/email/test/test_email.py
+++ b/Lib/email/test/test_email.py
@@ -2457,6 +2457,10 @@
     text/rfc822-headers
 """)
 
+    def test_make_msgid_domain(self):
+        self.assertEqual(
+            email.utils.make_msgid(domain='testdomain-string')[-19:],
+            '@testdomain-string>')
 
 
 # Test the iterator/generators