IP addresses are being banned by Fail2Ban on a Plesk server when working from Email Client

Symptoms

• When sending/receiving messages from Email Client (such as Outlook), the user's IP address is blocked by Fail2Ban
• From other IP addresses Plesk, websites and email accounts are accessible
• The IP address 203.0.113.2 can be found in Plesk at Tools & Settings > IP Address Banning (Fail2Ban) > Banned IP Addresses

Cause

The user IP address has been banned by fail2Ban "recidive" and "plesk-dovecot" jails because Email client actions are triggering false-positives on fail2ban.

Resolution

Apply one of the following solutions:

• Adjust fail2ban settings ban period and number of attempts before the ban to mitigate such false-positives: How to change the Fail2ban ban period and the number of attempts before the ban in Plesk?

• Add client IP to trusted IP-Addresses:

  Note: With the following solution, the problem may reoccur in case the client IP address will change.

  1. Connect to the server via SSH with a different IP address

  2. Open Tools & Settings > IP Address Banning (Fail2Ban) > Trusted IP Addresses > Add Trusted IP

  3. Add the IP address to be trusted in the text field IP address and click OK