Currently Being ModeratedJan 5, 2012 9:23 AM (in response to Darryl M)
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.
Currently Being ModeratedJan 6, 2012 5:02 PM (in response to MrHoffman)
But even with that aside, it still does not explain why the Domain Name in General settings changes, which it did during the night rendering all mail as 554 error. I've since went back to 10.5, at this point unless I can find a reason why it is happening, can't afford to remain booted into 10.6.
Currently Being ModeratedJul 24, 2012 11:58 PM (in response to Darryl M)
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.
Currently Being ModeratedJul 25, 2012 3:39 AM (in response to Douglas Urner)
I had tried multiple times to fix the issue but keeps coming back, even stripping the permissions off the file but it was still changing. I eventually went back to 10.5.8 and gave up on the 10.6.
Currently setting up a SAS RAID with Mtn Lion Server once it;s released and will give it another go but until then 10.5 is in use.
Currently Being ModeratedJul 26, 2012 6:40 AM (in response to Darryl M)
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.
Currently Being ModeratedJul 26, 2012 11:23 AM (in response to MrHoffman)
Should be: ..and other mail servers will often...
Currently Being ModeratedJul 26, 2012 4:16 PM (in response to MrHoffman)
Thank you very much for responding again, very appreciated.
Currently Being ModeratedJan 13, 2014 8:53 AM (in response to Douglas Urner)
I have exactly the same issue. Would you mind posting the script?
Currently Being ModeratedJan 14, 2014 6:44 AM (in response to marc herman)
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 @184.108.40.206 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.