Had a network that reinstalled it’s Exchange server. Actually, their whole domain. Their active directory went corrupt and they didn’t have a backup of the active directory so a reinstall happened. Anyway, Exchange was reinstalled and they could recieve email but not send. All the SMTP virtual server settings looked good but nothing. They would recieve the following errror:
“There was a SMTP communication problem with the recipient’s email server. Please contact your system administrator. Relaying not supported…”
The trouble was with the server IP. An additional IP address had been added to the server. That IP address needed to be added to the “allowed outgoing address” section of the spam filter.