[Dovecot] IMAP not working remotely

[Ondřej Bouda]

Hello,

I am trying to set up Dovecot 2.0.9 on Fedora 14. The problem I would like  
to ask for resolution is that IMAP is not working when connecting to the  
server from another network.

More precisely:
- POP3 is working entirely OK,
- IMAP is working OK when clients are connecting using local network  
addresses, like 192.168.0.100,
- when a client connects from outside, thus using remote IP address, or  
even from the server itself using the remote IP address of the server, the  
following happens: the client correctly connects, but the server sends no  
greeting (neither the configured login_greeting nor the server IMAP  
capabilities) and does not respond to the commands. In the server log, I  
get the following record a while after trying to connect (and actually  
trying to login):
Jul 08 23:24:16 imap-login: Info: Disconnected: Inactivity (no auth  
attempts): rip=<remote-server-address>, lip=192.168.0.100

Both routing and firewall are OK. The client really connects to dovecot  
(hence the log message), as seen from a telnet session:
Trying a.b.c.d...
Connected to example.tld (a.b.c.d).
Escape character is '^]'.
(and then nothing else)

The most confusing for me is the fact that POP3 is configured quite the  
same and works fine, as well as IMAP on the local network. I tried to  
change address in the inet_listener imap configuration, but if a wrong  
address setting was the cause, the client would not get connected at all.

As I have spent a pretty long time unsuccessfully searching for a cause, I  
am asking for some help.

Thanks for your time,
Ondrej Bouda



dovecot -n output follows:

# 2.0.9: /etc/dovecot/dovecot.conf
# OS: Linux 2.6.35.11-83.fc14.x86_64 x86_64 Fedora release 14 (Laughlin)  
ext4
auth_mechanisms = plain login cram-md5 digest-md5 ntlm
disable_plaintext_auth = no
first_valid_gid = 502
first_valid_uid = 502
last_valid_gid = 502
last_valid_uid = 502
log_path = /var/log/dovecot
login_greeting = Welcome
mail_location = maildir:/var/mail/virtual/%d/%n
passdb {
   args = scheme=plain username_format=%u /etc/dovecot/passwd
   driver = passwd-file
}
protocols = imap pop3
service auth {
   unix_listener /var/spool/postfix/private/auth {
     group = postfix
     mode = 0660
     user = postfix
   }
   user = dovecot-auth
}
service imap-login {
   inet_listener imap {
     address = *
     port = 143
   }
}
service pop3-login {
   inet_listener pop3 {
     address = *
     port = 110
   }
}
ssl = no
userdb {
   args = username_format=%u /etc/dovecot/passwd
   driver = passwd-file
}
protocol pop3 {
   pop3_client_workarounds = outlook-no-nuls oe-ns-eoh
   pop3_uidl_format = %08Xu%08Xv
}