A situation where the server is configured to loop back on itself was detected. If you have multiple SMTP virtual servers ...

{4}: A situation where the server is configured to loop back on itself was detected. If you have multiple SMTP virtual servers that are configured on your Exchange computer, make sure that they are serving unique incoming ports and that the outgoing SMTP port configuration is valid to avoid looping between local virtual servers. Check the configuration of the server's connectors for loops.