How I configured Thunderbird at Umea University
This worked for me in Ubuntu 13.04 on September 2013.
I assume that your CAS username is abcd1234, obviously it is not, so chage it everywhere
Account Actions -> Add mail account
Fill up the fields and continue (password is the CAS one)
Don't wait and hit Manual Config
Set incomming to IMAP, Server hostname to mail.ad.umu.se, port to 993, SSL to SSL/TLS and Authentication to Normal password
Set outgoing to SMTP, Server hostname to mail.ad.umu.se, port to 587, SSL to STARTTLS and Authentication to Normal password
Username is abcd1234 (your CAS log in).
You are now done!
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