i have a debian system with postfix, courier and mysql running.
Postfix works fine, courier looks good - no Log entrys with problems -
but i cannot connt to my mailbox. the clients like Squirrel mail say
"connection broken from imap", or thunderbird: "cannot conect"
In mail.log i see only (debug_login=1)

Nov  6 20:35:55 uranus couriertcpd: Connection, ip=[::ffff:127.0.0.1]
Nov  6 20:35:55 uranus couriertcpd: LOGIN: ip=[::ffff:127.0.0.1],
command=LOGIN
Nov  6 20:35:55 uranus couriertcpd: LOGIN: ip=[::ffff:127.0.0.1],
username=myn...@mydomain.com

I have try so many things. i think, it cant be a auth problem. this is
working.
it must be deeper ;(
I have no iptables (firewall) running,
via Telnet localhost 143 i get

:~# telnet localhost 143
Trying 127.0.0.1...
Connected to localhost.
Escape character is '^]'.
* OK [CAPABILITY IMAP4rev1 NAMESPACE AUTH=CRAM-MD5 CHILDREN IDLE QUOTA
SORT THREAD=ORDEREDSUBJECT THREAD=REFERENCES UIDPLUS STARTTLS] Courier-
IMAP ready. Copyright 1998-2008 Double Precision, Inc.  See COPYING
for distribution information.

Please, please help ;)