After several months of trying various things, giving up, trying again … etc. My connection issues with Mail.app and my mail server are fixed. Turns out that my mail server (exim) didn’t like the IPV6 address that mail.app was for some reason feeding it. I was getting “syntactically invalid argument(s): [?\031?\033???IPv6:::1]”. Commenting out the IPV6 loopback (::1) in my /etc/hosts file fixed it. Thanks to the comments at the end of http://www.oreillynet.com/sysadmin/blog/2006/03/ssh_tunnelling_apple_mail.html for the solution
Written on March 10th, 2007 by Chris Prather