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unable to receive external email

329 Views 4 Replies Latest reply: Feb 10, 2013 2:08 AM by Camelot RSS
Thin&Hungry Calculating status...
Currently Being Moderated
Feb 6, 2013 2:56 PM

I've been running OS X Lion Server for about a year or more now on a mac mini. Mail service has been chugging away just fine until this morning when it stopped delivering emails from outside our domain to the users' inboxes. Email sent internally, from within the same domain, gets delivered just fine. And users can send emails both internally and externally.  But users can receive mail only from within the same domain.


I have checked as many logs as I could think of and see nothing out of the ordinary. IMAP is running fine, postfix appears to be running without notable incident (though if I should be checking that more thoroughly, I'd take advice on how to do so - I've only checked the Mail log).


Senders do not get any notification of failure. And I do not see any errors in Server (nor in Perhaps I am not looking in the right places?


I even checked DNS, and the log there shows a ton of errors (connection refused), so I added a couple of new forwarded IP's just in case that might help. This may be a sign of my desperation, especially because the DNS should have little to do with email finding its way to my server. But I'm getting desperate.


Any advice and assistance is gratefully accepted.

  • Camelot Level 8 Level 8 (45,670 points)
    Currently Being Moderated
    Feb 6, 2013 9:13 PM (in response to Thin&Hungry)

    Well, for one, this statement is completely wrong:


    DNS should have little to do with email finding its way to my server


    Mail is as dependent on DNS as anything else - maybe more so with the dependence on MX records. If your DNS isn't working, remote servers might not know where to send the mail.


    What's missing from your post, though, is what you DO see in the logs. Do you see connections from the outside world? Does your server accept those messages? does it reject them? why?


    If the server isn't getting connections from the outside world then either your DNS is broken (see my point above), or there's some network-level issue such as a firewall policy, a NAT port mapping or some such that's preventing external servers from connecting.


    It would help if you posted the domain name since that would at least let others here test the server and report back what we see. As it is we're working blind and can only offer WAGs as to what the problem might be.

  • Camelot Level 8 Level 8 (45,670 points)
    Currently Being Moderated
    Feb 10, 2013 2:08 AM (in response to Thin&Hungry)

    Port blocking by your ISP seems like a likely issue.


    You'll clearly need to talk to them to find out the change. You might need to check the terms of your service with them - some ISPs prohibit running your own mail server on their network due to spam origination issues... and they might have blocked you because you hit some threshold and popped up on their radar. It might also be an error.


    Even if they do unblock port 25 you're doing to need to talk to them about reverse DNS. Right now your reverse DNS does not map back to your domain (it maps to a generic hostname in your ISP's domain), and that's going to cause you a world of hurt as far as email is concerned. You may need them to setup reverse DNS, or act as a mail proxy/gateway for you to avoid such issues.


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