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I have hMailServer installed on Windows Server 2008. It's all set up and working, except that I can't send mail from it through Thunderbird (getting an SMTP timeout message) from my own PC (which is not in local network with the server). I have checked the settings multiple times, and they are correct. With a non-standard port (as in, not 25), I could send mail, but due to it being non-standard, those mails never got to the recipients.

Telnetting to the server through port 25 works. The ports are open from the firewall. Sending mail "locally" from the server works (and auto-reply works). My Thunderbird settings let me authenticate and send mail when the SMTP server is using a non-default port, but not when it's using 25, the default port. I can access other SMTP servers all fine through 25, and disabling my own firewall didn't help.

The exact error message is this (mind the Finnish at the start):

Postia lähetettäessä tapahtui virhe: postipalvelimen kättelyviesti oli virheellinen: Cannot connect to SMTP server (, connect timeout

Repeating, I can connect to it when the port is not 25. I do not have hardware firewall at the moment, which could prevent that.

Any help would be appreaciated!

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Check your anti-virus/malware software (if you have any installed) which may be installed on the system. They have a tendency to intercept the common application ports in order to hijack them for their protection services.

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I disabled my Anti-Virus and the server's Anti-Virus, but still can't send mail through that server. Thanks for the help, though. – Miikka Virtanen Jul 13 '11 at 11:35
What is actually displayed when you telnet from the problematic system to the server on port 25? – user48838 Jul 13 '11 at 12:30
220 ESMTP - and I can continue with e.g. HELO – Miikka Virtanen Jul 13 '11 at 13:56
Is that the exact same banner when you have things set for a non-SMTP port? – user48838 Jul 14 '11 at 12:36
Yeah, it's the same one. – Miikka Virtanen Jul 14 '11 at 14:05
up vote 0 down vote accepted

Alright, solved my problem. Apparently, my ISP is blocking the port 25, and I was using SSL and the port 465 with other mail servers. Added an additional (non-25) port for the SMTP server now, so that it can still communicate on 25 and the new one.

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