I am running an Exchange Server SP2 single mail server. We can send email but all clients that try to send us emails are getting messages back saying"
Diagnostic-Code: smtp;553 Relaying is not supported
The only recent change is that we installed Trend Micro Worry Free Business Security Advanced about a week ago but the issue just started yesterday monring. It seems like our mail server is rejecting recipients because it thinks the email is being relayed but every single email is being rejected, even from domains that we know are not relaying email. ESM Message Tracking does not show me what is happening when the senders attempt to send emails. It seems like it is not even reaching the Exchange server at all. Please help.