[Dovecot] Dovecot login hangs often

[P P Anwar]

Hi -

We have dovecot version : 0.99.11 release : 2.EL4.1 on Centos 4.2,
with an LDAP backend (Samba PDC) and pam set to authenticate against
LDAP.  Dovecot is set to use pam for authentication.  It uses mbox,
and the machine has very little load (95% idle, no memory pressure).

Every 36 hours or so, no users are able to login to imap (we have only
imap enabled).  Other services that use the same backend are working
fine (like squid and ssh logins) even while this is happening.  So we
are not sure if we can blame this on pam/ldap problems.

When this happens, we tried a "service dovecot restart", and that
results in saying the "address is in use".  About 10 "imap-login"
processes seem to lurk around holding on to the imap port.  We can get
dovecot service to start again, only after a "killall -9 imap-login".

What kind of debug should we enable so that you all can diagnose this
further ?  Any other configuration things that we should try ?   We
prefer to stay with Redhat/Centos releases, but if this is already
reportedly fixed in one of the later builds, we are open to trying
one.

Regards,
Anwar.