Dear Sir/Madam We have an exchange server 2003 configured for our email purpose, i am getting frequently problem, and the error code is: 550 5.7.1 Unable to relay. So please provide some help on this. Thank You

Who is getting this error and in what circumstance?

Dear Andy David Actually from our email server, we can't send mail to gmail and hotmail domain. We are not getting any bounce emails and any alerts report. But recipients would not receive the mail that the sender sends to recipient gmail or hotmail account. So i tested online SMTP Test Utils on that i used to get that error code 550 5.7.1 Unable to relay. So thought that there is some issue on the exchange. So can you please provide some solution in this matter. IT will be great help. Thank You

Ok, I would enable SMTP protocol logging and send test messages to those domains, then check the logs to get a better idea on why they are being rejected. Post them here as well if you have any additional questions:http://support.microsoft.com/kb/265139How to enable SMTP protocol logging in Exchange 2000 Server and in Exchange Server 2003

Ok, that will be good steps to verify that issue. I also be looking forward to solve this issue. ThanK You.

More resources: Troubleshooting Mail Flow and SMTP How to troubleshoot mail relay issues in Exchange Server 2003 and in Exchange 2000 Server