Office 365 with Exchange2010 and 2013 coexistence mail flow issue


  • I have Exchange 2010 and Exchange 2013 with O365 Hybrid configured on Exchange 2013.

    When a 2013 user send email internal and external it works fine but when a 2010 user send email it will get queued up.

    If I tick the Exchange server authentication and change the FQDN to internal FQDN of Default frontend connector(Exchange2013) all mail goes from Exchange 2010 to 2013 and goes out but email from O365 will not receive until I change it back to the external FQDN (I.e

    How to fix this issue?

    Thanks, MAS
    Please mark as helpful if you find my comment helpful or as an answer if it does answer your question. That will encourage me - and others - to take time out to help you.

    Wednesday, July 5, 2017 12:00 PM


  • The Hybrid Configuration Wizard creates new send and receive connectors for all traffic to and from Exchange Online.  If the two Exchange servers in your organization won't talk to each other, it's probably because someone messed with the default receive connector.  ExchangeServers is required for two Exchange servers to communicate with each other, and that right was assigned to your default receive connector when it was created during installation. 

    Without being able to examine your connectors, I can't say how your connectors have been screwed up, but the general advice I would give you is to put the Default Frontend connector back to the default settings and create a new connector if you need one with any special configuration settings.

    Ed Crowley MVP "There are seldom good technological solutions to behavioral problems."
    Celebrating 20 years of providing Exchange peer support!

    Wednesday, July 5, 2017 11:14 PM