Hello John,
1) run 2 instances of imapd
2) proxy server http://www.vergenet.net/linux/perdition/
3) Patching to pass source IP address to courier-authdaemon...
There have been patches posted to this list several times in the past
which pass the source IP address to courier-authdaemon, and
I'm happy to announce experimental support for SSL certificate-based
authentication.
Download: http://www.courier-mta.org/download.php#authlib
Download: http://www.courier-mta.org/download.php#imap
A full Courier build, with SSL certificate-based authentication for SMTP, is
TBD.