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SBS 2008 SMTP SmartHost Setup - IP address works, FQDN does not - WHY?

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  • SBS 2008 SMTP SmartHost Setup - IP address works, FQDN does not - WHY?

    Hello, I'm a new member here! I've read some great info here and hope to contribute

    I am setting up a SMTP send connector on SBS 2008 - all outgoing mail will use this send connector. My domain name is managed by Gate.com. My SMTP server for outgoing mail is smtp.mydomain.com (this is a Gate.com server). In SBS, when I specify "smtp.mydomain.com" as the smarthost, outgoing mail fails.

    From the logs, I see that SBS is actually trying to connect to mx.mydomain.com. I can tell this because in the log I see the IP address that resolves to mx.mydomain.com.

    If I specify the IP address of smtp.mydomain.com (instead of the FQDN), everything works.

    I prefer to use "smtp.mydomain.com" versus the IP address. Do you know why I cannot, and why the IP address of the mx server is being used? It's as if smtp.mydomain.com thinks I'm trying to deliver mail versus relay?

    Thanks!

  • #2
    Re: SBS 2008 SMTP SmartHost Setup - IP address works, FQDN does not - WHY?

    Is your internal domain the same as your external domain?
    Does the MX host name and the SMTP host name resolve to the same IP address? Not unusual if it does.

    Simon.
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    Simon Butler
    Exchange MVP

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    • #3
      Re: SBS 2008 SMTP SmartHost Setup - IP address works, FQDN does not - WHY?

      No, my internal domain is mydomain.local, whereas my external domain is mydomain.com.

      smtp.mydomain.com is the SMTP server that my domain/web host provider has me use (for POP3 clients such as Outlook Express, for example). It's IP address is _not_ the same as the IP for mx.mydomain.com.

      Anyways, using the IP address of smtp.mydomain.com as the smarthost works, so I will just use that for now.

      It's weird that using the FQDN (smtp.mydomain.com) does not work. Like I said, in the logs I can see it sending EHLO to the IP of mx.mydomain.com.

      Thanks!

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      • #4
        Re: SBS 2008 SMTP SmartHost Setup - IP address works, FQDN does not - WHY?

        Open a command prompt and do an NSLOOKUP for both smtp.mydomain.com and mx.mydomain.com and ensure that they resolve to the correct IP addresses. If they do then I have no clue; if they don't then DNS is fubarred somewhere.
        TIA

        Steven Teiger [SBS-MVP(2003-2009)]
        http://www.wintra.co.il/
        sigpic
        Iím honoured to have been selected for the SMB 150 list for 2013. This is the third time in succession (no logo available for 2011) that I have been honoured with this award.

        We donít stop playing because we grow old, we grow old because we stop playing.

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