GWIA will not receive inbound email. Outbound email works fine. Unable to telnet to <GWIA IP Address> 25, error 554 IP connection rejected
Possible corrupt or damaged gwac.db file.
In the GWIA properties | Access Control | Settings | Default Class of Service | SMTP Incoming, select Prevent Incoming Messages and save the change.
Then select Allow Incoming Messages and save the change.
Toggling this setting will trigger an update in the gwac.db file which might allow the GWIA to begin processing inbound messages again.