550 550 5.7.1 Unable to relay for

If you found this error in the Smartermail logs and you are using IIS 7 and IIS 6, find below for the solution:
1. RDC to the server and go to IIS 6
2. Right click on the SMTP and stop the service
3. Right click SMTP and then open Properties, change the port number to 587
4. Restared Smartermail service for the server and later start the SMTP service in IIS 6
That’s it.

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