So, just worked my way through the EXCELLENT guide for setting up an Postfix/Dovecot email server. Everything appears to work fine and I can mutt in locally and I can mutt in over IMAPS remotely. However, I can't get Thunderbird to connect. I've tried all kinds of different combinations and none works. Any clue what I might be missing?

Note, I do see this in my logs when I last failed to connect from Thunderbird:

Dec 1 22:12:08 myhostname dovecot: imap-login: Disconnected (no auth attempts in 0 secs): user=<>, rip=my remote IP, lip=my linode IP, TLS: SSL_read() failed: error:14094418:SSL routines:SSL3_READ_BYTES:tlsv1 alert unknown ca: SSL alert number 48, session=<h2dD7jMJ/ABAlzP6>

I've seen some web forum comments about Thunderbird rejecting my default dovecot.pem cert, but I don't know if that's accurate.

I resolved using 3 things. Not sure the first 2 had any bearing:

1. Reconfigured dovecot's 20-imap.conf file to turn on the Thunderbird workaround tb-extra-mailbox-sep
2. Turned off OCSP under thunderbird's Advanced->Validation settings
3. Used settings similar to these:

IMAP server: mail.somedomain.com
Port: 993
Security: SSL/TLS
Authentication Method: normal password
Username: dickie@somedomain.com
SMTP server: mail.somedomain.com
Port: 587
Security: STARTTLS
Authentication Method: normal password
Username: dickie@somedomain.com

Note, do NOT try to test or retest your settings! Just go straight to 'Done'. You'll get a prompt to ignore the cert (heart of the problem?).