Somebody in the thread at some point said:
So my best guess is that there is something wrong
with my dovecot configuration.
I "yum remove"d and "yum install"ed dovecot
(and re-edited dovecot.conf),
but that didn't seem to make any difference.
Anything in /var/log/maillog when you start Dovecot? /var/log/messages?
The ssh tunnel will change the landscape for networking issues because
it will seem to Dovecot you are coming from localhost. But if Dovecot
is unhappy or dead it won't change that.
-Andy