How do I allow non-domain servers to SMTP relay through my Exchange 2013 Hybrid environment?


  • I currently have a hybrid environment with Office 365 and Exchange 2013 where all mailboxes reside in 365 but Exchange is used for SMTP relay of various applications/devices. Up until now everything that has had to utilize SMTP relay has been on our internal network so I setup the receive connectors on the CAS servers but now we need some non-domain joined application servers in azure to be able to SMTP relay and I can't seem to get it to work. I created a receive connector on the edge server for relay, added the necessary remoteIPRanges for the application servers but when testing with a simple send-mailmessage command in powershell I receive the following error "Send-MailMessage : Unable to connect to the remote server".

    Is it because it only has the Hub Transport role installed or possibly because the permission group is only set to AnonymousUsers rather than AnonymousUsers and Custom like my CAS servers are?  Any help would be greatly appreciated. 

    Thursday, August 4, 2016 5:18 PM


All replies

  • Hi

    can you telnet to the edge box? what errors you getting in the event logs? user not authenticated?

    Edward van Biljon - Exchange MVP

    Thursday, August 4, 2016 5:35 PM
  • Hi Edward, 

    I actually am not able to telnet over port 25 to my Edge server. I've verified the ports are open so I will continue investigating this for the time being and respond once I have something. Thank you.

    Thursday, August 4, 2016 5:49 PM
  • Hi there

    do you have Anti-Virus running on the Exchange server or any firewalls that could be stopping inbound traffic?

    As a test can you telnet out of the edge box to another server running exchange on port 25?

    Edward van Biljon - Exchange MVP

    Thursday, August 4, 2016 5:53 PM
  • It looks like it was a NAT problem. Thanks. 
    Thursday, August 4, 2016 6:32 PM
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    Friday, August 5, 2016 8:08 AM