diff --git a/hgext/patchbomb.py b/hgext/patchbomb.py
--- a/hgext/patchbomb.py
+++ b/hgext/patchbomb.py
@@ -818,6 +818,8 @@
             generator = emailgen.Generator(_bytesgenerator(fp),
                                            mangle_from_=False)
             generator.flatten(m, 0)
-            sendmail(sender_addr, to + bcc + cc, fp.getvalue())
+            alldests = to + bcc + cc
+            alldests = [encoding.strfromlocal(d) for d in alldests]
+            sendmail(sender_addr, alldests, fp.getvalue())
 
     progress.complete()