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Dovecot is a POP3/IMAP server that can also provide authentication for SMTP and other SASL services. See also the Fail2Ban page on the Dovecot wiki.

Dovecot-1.0.0 with pam. Other authentication mechanism probably produce different output.

  • Jan 11 03:42:09 email dovecot: auth(default): pam(, pam_authenticate() failed: User not known to the underlying authentication module
  • Jan 26 22:31:37 email dovecot: auth(default): pam(dan, pam_authenticate() failed: Authentication failure

Dovecot-1.0.15 with sql, and "auth_verbose = yes":

  • Jan 11 03:42:09 email dovecot: auth-worker(default): sql(, Password mismatch
  • Jan 11 03:45:09 email dovecot: auth-worker(default): sql(someoneelse, unknown user

With successfull logins, it doesn't print anything from "auth-worker".

Dovecot-1.2.13, without pam (slackware), with TLS :

  • Jul 31 13:53:08 email dovecot: imap-login: Aborted login (auth failed, 1 attempts): user=<someone>, method=PLAIN, rip=, lip=, TLS
  • Jul 31 13:54:35 email dovecot: imap-login: Disconnected (tried to use unsupported auth mechanism): user=<someone>, method=LOGIN, rip=, lip=, TLS: Disconnected

(rip is the IP address of the client, lip is the IP address of the server) Same results with "auth_verbose = yes".


The regular expressions below are proposed failregex for this software. Multiple regular expressions for failregex will only work with a version of Fail2ban greater than or equal to 0.7.6.

The tag <HOST> in the regular expressions below is just an alias for (?:::f{4,6}:)?(?P<host>\S+). The replacement is done automatically by Fail2ban when adding the regular expression. At the moment, exactly one named group host or <HOST> tag must be present in each regular expression.

Please, before editing this section, propose your changes in the discussion page first.

failregex = dovecot.*auth\(default\): pam\(.*,<HOST>\): pam_authenticate\(\) failed: