You can check all fail2ban jails with:
fail2ban-client status
And unblock ip with:
fail2ban-client set {jail} unbanip {ip address}
in your case
fail2ban-client set postfix-iredmail unbanip {ip address}
You can check all fail2ban jails with:
fail2ban-client status
And unblock ip with:
fail2ban-client set {jail} unbanip {ip address}
in your case
fail2ban-client set postfix-iredmail unbanip {ip address}