Auth.log chyby Postfix+Cyrus

V logu /var/log/auth.log mam neustale nasledujici vypisy:
Nov 1 11:19:50 apps PAM_unix[2017]: authentication failure; (uid=0) -> 925 for imap service
Nov 1 11:19:50 apps PAM_unix[1938]: check pass; user unknown
Nov 1 11:19:50 apps PAM_unix[1938]: authentication failure; (uid=0) -> 756 for imap service
Nov 1 11:19:50 apps PAM_unix[1928]: check pass; user unknown.
. .
Nov 1 11:19:50 apps PAM_unix[1928]: authentication failure; (uid=0) - 687 for imap service
Nov 1 11:19:51 apps PAM_unix[2018]: check pass; user unknown
. .
Nov 1 11:19:52 apps cyrus/imapd[9541]: can't access srvtab file /etc/srvtab: No such file or directory
Nov 1 11:19:52 apps cyrus/imapd[9541]: server add_plugin entry_point error generic failure
Nov 1 11:19:52 apps cyrus/imapd[9541]: _sasl_plugin_load failed on sasl_server_plug_init for plugin: kerberos4
Nov 1 11:19:52 apps cyrus/imapd[9543]: can't access srvtab file /etc/srvtab: No such file or directory
Nov 1 11:19:52 apps cyrus/imapd[9543]: server add_plugin entry_point error generic failure
Nov 1 11:19:52 apps cyrus/imapd[9543]: _sasl_plugin_load failed on sasl_server_plug_init for plugin: kerberos4
Nov 1 11:19:52 apps PAM_unix[1948]: check pass; user unknown
Nov 1 11:19:52 apps PAM_unix[1948]: authentication failure; (uid=0) - 655 for imap service

Muzete mi pomoct kde mam hledat zdroj techto hlaseni?

Dotaz: Auth.log chyby Postfix+Cyrus