Especially some imap/pop3 login bursts could have caused errors like: imap-login: Error: net_connect_unix(imap) failed: Resource temporarily unavailable
Fix in http://hg.dovecot.org/dovecot-2.2/rev/69179ca6007d Explanation & workaround in http://wiki2.dovecot.org/SocketUnavailable : Dovecot v2.2.0 - v2.2.6 were attempting to optimize host.domain lookups by doing them only once in the master process. Unfortunately they were actually doing the lookup every time when creating a new process. In some configuration this lookup could have done a somewhat slow DNS lookup, causing the process creation to become very slow and triggering this message. The fix is in v2.2.7 and you can also workaround this: • Add to dovecof.conf: import_environment = TZ DEBUG_OUTOFMEM DOVECOT_HOSTDOMAIN • Before "dovecot" binary is started, run: export DOVECOT_HOSTDOMAIN=mailserver.example.com (of course changing the value)
