I ran into this bug using bzr_hookless_email, fortunately someone had published a patch which seems to have fixed the issue:
=== modified file 'bzr_hookless_email.py'
--- bzr_hookless_email.py 2012-03-22 15:15:15 +0000
+++ bzr_hookless_email.py 2012-04-25 06:05:55 +0000
@@ -159,7 +159,7 @@
self._config = self._branch.get_config()
def update(self):
- smtp = SMTPConnection(self._config)
+ smtp = SMTPConnection(self._branch.get_config_stack())
smtp_from = None
for revision in self._revisions_to_send():
msg = self._compose_email(revision)