Find out the banned IP.
vi /var/log/fail2ban.log
Unblock the IP
fail2ban-client set roundcube unbanip 123.200.16.218 fail2ban-client set recidive unbanip 123.200.16.218 fail2ban-client set postfix unbanip 123.200.16.218 fail2ban-client set dovecot unbanip 123.200.16.218 fail2ban-client set pregreet unbanip 123.200.16.218
That’s All!