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I'm using Windows Server 2008 R2, and Xampp with mercury mail. My problem is that I can't send mails via my server outside the server network.

  • My SMTP server is using port 25, which is open and accesible outside the local network. But telnet domain.com 25 says, can't connect (I also tested with firewall off)

  • When thunderbird trying to connect it's only timing out. (used mail.domain.com but tryed a lot of variations too for example: smtp.)

  • I tested almost all available setting in mercury without luck, the only option what i dont understand the : "IP interface to use" what i left blank. I also added Resiriction to my ip in connection control tab.

    • And one more curious thing that imap server is accessible without any problem (local/nonlocal).
    • SMTP server is accessible via local network.

Anyone has any idea what can be the problem ? Or can me suggest anything what help me troubleshoot the problem? My main problem is that I don't know what's happening, coz nothing in mercury log and I only get timed out message without any useful info.

user163810
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ISPs often really like to block port 25. This happens on connections from residential dialup to IP transit in datacentres. You might need to chat with whoever is providing your upstream and let them know you're running an SMTP server.

While you're doing that, make sure you have rDNS set up, SPF (and optionally DKIM) set up properly, and aren't on any RBLs.

Falcon Momot
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  • They said they are not blocking any port. rDNS set up is fine and aren't on RBLs. Any other idea? The strange part is that I can connect imap outside localhost, but not smtp, and I can connect smtp from localhost, but port 25 is open so somehow it doesn't find smtp server outside local network – user163810 Oct 08 '13 at 11:56
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    You was right, Port 25 was blocked by ISP, just they lied to me it seems. Now it's working property on port 26. Problem solved, thank you. – user163810 Oct 08 '13 at 13:33