I had a similar problem and solved it by making sure my Debian certs (Exim4/Courier) were created using the same domain name as I was configuring in Mail.app. Then I deleted all of the old entries from the Mac keychain and everything worked perfectly.
Cheers, Keith -- To UNSUBSCRIBE, email to debian-bugs-dist-requ...@lists.debian.org with a subject of "unsubscribe". Trouble? Contact listmas...@lists.debian.org
