Add signature: Courier imapd/pop3d

[Former user]

Jun 24 15:34:21 mail imapd: LOGIN FAILED, user=[e-mail], ip=[::ffff:92.63.193.55]

Jun 24 11:53:25 mail pop3d: LOGIN FAILED, user=britton, ip=[::ffff:121.226.61.81]

(process may show up in logs as imapd-ssl or pop3d-ssl)

Jun 24 14:33:29 mail postfix/smtpd[756]: warning: unknown[185.156.173.140]: SASL LOGIN authentication failed: authentication failure

Jun 24 14:40:28 mail postfix/smtpd[1571]: warning: vps1644727.vs.webtropia-customer.com[185.15.244.156]: SASL LOGIN authentication failed: authentication failure

[Kevin Zheng]

Latter two attacks for postfix are already correctly detected.

[Kevin Zheng]

Fixed in b8a949b8.

[Kevin Zheng]

Removing version: 2.1 (automated comment)