Smartermail will not receive incoming email, fails the telnet 25 connection test.

Problem reported by William Maybaum - 4/8/2026 at 8:38 AM

Submitted

I am trying to setup Smartermail on my server. I do not know how to diagnose the problem, then fix it.

Thanks,

Bill

8 Replies

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J. LaDow Replied

4/8/2026 at 8:48 AM

You have a firewall, traffic routing problem, or SmarterMail configuration problem if port 25 is not responding.

That's the best anyone will be able to tell you without knowing more about what you've already configured and tried to resolve.

More info here:

https://portal.smartertools.com/kb/a2646/cannot-receive-mail-messages.aspx

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William Maybaum Replied

4/8/2026 at 11:52 AM

I have checked the firewall and port forwarding 25 is open to localhost (127.0.0.1). Smartermail is listening on the LAN (192.168.1.41) and local host. I checked the router for port forwarding and the firewall both look Ok. The server has inbound rules to open the ports for Smartermail.

Heimir Eidskrem Replied

4/8/2026 at 12:01 PM

can you telnet to the server on 192.168.1.41 from your local network?

J. LaDow Replied

4/8/2026 at 12:37 PM

Your transit provider could be blocking port 25 (especially if the test from Heimir passes).

If you can telnet to it on the local LAN, but not via the external IP then either the transit provider has it blocked or NAT translation/routing is broken (includes firewall issues on the external interface).

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William Maybaum Replied

4/9/2026 at 6:16 AM

I checked it is being blocked on the local lan connection. I received an update from Smartermail support with some updates to investigate.

Thanks for your support.

Heimir Eidskrem Replied

4/9/2026 at 6:26 AM

Its blocked on the LAN connection then turn off the firewall and try it again. also make sure you dont have malware protection that blocks it.

If it responds after turning off the firewall then your firewall isnt configured correctly.

Is this a windows server?

William Maybaum Replied

4/9/2026 at 10:13 AM

It is a windows server. I will check it out. It seems risky to turn off the firewall, I understand the need for the test. Will try to be quick. LOL

Thanks,

Bill

J. LaDow Replied

4/9/2026 at 11:48 AM

Just create a rule that opens the ports you need:

80,443,25 (SMTP),110 (POP),143 (IMAP),465 (SMTPS CLIENTS), 587 (SMTP SUBMISSION for clients), 990 (POPS), 993 (IMAPS)

That would be the standard practice, anyways...

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