[Dovecot] unable to lock for exclusive access: Resource temporarily unavailable

[Timo Sirainen]

On 25.9.2013, at 10.27, Nikos Papadopoulos <npap at ecs.gr> wrote:

> We have a mail server (RHEL 6.0, Postfix and Dovecot 1.0.7).
> 
> mail_location: mbox:~/mail:INBOX=/var/mail/%u
> 
> There is great delay in the delivery of the emails. Some seem to not be
> delivered at all. Issuing the mailq command we get the following message for
> almost all the email accounts:
> 
> (cannot update mailbox /var/mail/xyz for user xyz. unable to lock for
> exclusive access: Resource temporarily unavailable)

mbox format is problematic in this way. Newer Dovecot versions (v2.x) do some extra work to unlock the mbox earlier with POP3. That might help you. Or you could switch to Maildir format where this isn't a problem. I'm not sure why it started happening only now and not earlier. Perhaps the POP3 clients are downloading mails more slowly, perhaps you're getting more mail and things are running slower than before.