I manage a 2010 Exchange Server that has developed a problem. The server cannot connect to a specific domain to send email. The other domain can send to us. This seems to only effect a single domain.
I am struggling to understand the detail of the problem. Changing the logging to verbose has these error
452 4.3.1 Insufficient system resources,
503 5.5.2 Need mail command,
I understand that this points to back pressure but I cannot see any stress on the server.
I cannot seem to identify it the error is with my server and isp internet problem or an issue with the other domain