This procedure requires the authorized server administrator on a supported Plesk for Linux installation. Obtain the actual client public IP, affected service, time and error. Keep a console or alternate authorized access route if your own administration address is blocked.

1. Open Tools & Settings > IP Address Banning and inspect the banned-address list and relevant jail information.
2. Match the address and time to service logs. Determine whether the failures came from a legitimate user, a stale device credential, automation or hostile activity.
3. Correct the source of legitimate failures before removing the ban. Update all affected mail clients or scheduled connections, including devices that may retry in the background.
4. Unban only the verified address through the supported control. Use a trusted-address exception only for a justified, controlled network and review its scope; broad allowlists weaken protection.
5. Test one legitimate connection and watch the logs for renewed failures or a repeated ban. Keep the protection enabled while resolving the cause.

Confirm the intended user can connect and the jail continues detecting unrelated failures. Check that the public IP has not changed during the investigation. Record why an exception was added and when it will be reviewed.

If the address is not listed, inspect upstream firewalls, hosting-provider controls, application blocking and service availability. Do not disable Fail2Ban globally to diagnose one account. If the same address is repeatedly blocked, find every retrying client rather than extending an unlimited exception.

• Protecting a Plesk account with two-factor authentication
• Diagnosing website errors with the Plesk log browser
• Changing a mailbox password in Plesk
• Adding supported Apache and nginx directives in Plesk

• Plesk: Protection Against Brute Force Attacks
• Plesk: IP Ban IP Address Banning Fail2ban