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I have a OS X Server behind a router. Server's ip address is The router has open ports on everything and an external ip.

I've setup my mail exchange. I can receive mail people send to me but the reply never gets back to them.

I don't use TXT records, could that be the problem? Could my ISP be blocking something?

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Have you looked at /var/log/mail.log on your server? – cjc Nov 12 '12 at 12:37
  • Check your FCrDNS to ensure you aren't getting binned as spam. You should also confirm how your server identifies itself to the outside world by telnetting to port 25 on your server and checking the banner.

  • Further to spam issues, run your IP through MultiRBL

  • Ensure you can telnet from your server to a known-good remote mailserver on port 25 (e.g.

  • What do your mail logs say? These should be in /var/log/maillog (or mail.log).

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telnet: connect to address 5.x.x.x: Operation timed out telnet: Unable to connect to remote host I'm able to connect to apache http server just fine. I think my ISP is blocking port 25! – unmircea Jun 9 '14 at 10:38

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