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Changing default gateway cause problems

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  • Changing default gateway cause problems

    Here's my scenario:

    1 Exchange 2003 server...manually assigned static IP address and default gateway. Pretty basic setup. We have OWA with FBA, activesync. All traffic going through a firewall. Incoming SMTP forwarding to exchange server. All email is sent to a 3rd party smarthost that does all of our spam/virus filtering, archiving (done via POP3)...MX records pointing to that smarthost for incoming email as well.

    Recently, we installed a new ISP...mainly for internet traffic. I set it as the new default gateway on the domain. I wanted to also send email traffic through this gateway.

    Problem is, when I change the default gateway on the Exchange Server to the new gateway, OWA, activesync, POP3 mail all stop working! I can see, mail is actually being sent, but nothing can make it in.

    I can browse OWA using the internal server name and internal email flows fine. I change the default gateway back and everything works fine.

    I tried also adding a static route to my smarthosts...same symptoms.

    Any ideas or suggestions for troubleshooting?

  • #2
    Re: Changing default gateway cause problems

    That is the expected behaviour.
    To correctly receive inbound traffic the default gateway needs to point a the same place where the traffic is originating. Unless you can control 100% where all traffic is coming from you will be unable to change the default gateway on the Exchange server and receive email correctly.

    Simon Butler
    Exchange MVP

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