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General Mail Settings Changing Automatically - Server

1630 Views 23 Replies Latest reply: Jan 14, 2014 6:44 AM by MrHoffman RSS
  • MrHoffman Level 6 Level 6 (11,695 points)

    If the ISP won't change the reverse DNS, then you won't encounter reliable mail traffic without using an (authorized) SMTP relay through another SMTP server.


    Your SMTP server will be indistinguishable from a spam SMTP server, and many other SMTP servers will not communicate with it.

  • Douglas Urner Level 1 Level 1 (15 points)

    Did you ever figure out a solution to this?


    I'm seeing a similar problem with 10.6.8, it seems to happen whenever my DSL line goes down and then back up. My "solution" at this point is to use a script which watches the file and puts it back whenever it changes.

  • MrHoffman Level 6 Level 6 (11,695 points)

    Having valid DNS is part of the SMTP RFCs.  Mountain Lion and Mountain Lion Server will (still) require valid DNS configuration, and other DNS servers will often not respond to a mail server with mismatched reverse DNS; the other servers can drop arriving messages, and may not send messages to the server. 


    For a related discussion, one of the folks posting here, Douglas Urner, has a related thread on this question.

  • MrHoffman Level 6 Level 6 (11,695 points)

    Should be:  ..and other mail servers will often...

  • marc herman Level 1 Level 1 (30 points)

    I have exactly the same issue. Would you mind posting the script?

  • MrHoffman Level 6 Level 6 (11,695 points)

    Please establish correct local DNS, and establish correct public DNS.


    DNS is absolutely critical to a properly-functioning mail server, and misconfigured DNS will cause your messages to be dropped by other servers, and there is absolutely nothing you can do here to prevent other mail servers from discarding your outbound mail, other than either fixing DNS, or using a mail relay. 


    When operating in a NAT'd network, incorrect local DNS will cause the mail server to get confused about its identity.


    Any script that tries to reset the settings when the mail server gets confused by invalid DNS is somewhat of a hack, and the configuration will probably still have transient problems.  This in addition to seeing your outbound mail discarded by other mail servers, and some servers refusing to send your server messages.


    If you post your (public) domain, somebody here can check it.   If you're shy about posting that, there are mail- and DNS-related threads here, here, and here — which describe how to verify public DNS.  You'll need to bypass your local DNS to check your public DNS; adding @ on the dig query causes the dig command to bypass local (NAT'd) DNS and connect to Google DNS.  Private DNS is verified with the sudo changeip -checkhostname mentioned earlier, and with the local dig commands.

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