Cannot telnet into mail server (SMTP)

[suklee]

My server runs Mdaemon and is behind a firewall. I have opened all necessary ports on the router to its internal IP address, eg. 143 (IMAP), 25 (SMTP), 110 (POP3), 80 (WorldClient), etc.

On the internal LAN, no problems whatsoever sending and receiving.

Once out of the LAN, I am getting some really weird behavior.

From home, I can connect to our server via IMAP and view messages without problem.

Sending gives me headaches, however. Cannot seem to connect to port 25; I will always timeout with "could not open connection to the host, on port 25: connection failed". Even stranger, I asked a friend to try telneting from his office, and he was able to connect! (220 company.mail ESMTP MDaemon .... )

telnet mail.mydomain.com 25 will give me timeout error at home
telnet mail.mydomain.com 143 will connect
telnet mail.mydomain.com 110 also ok

Why am I unable to connect at home, while my friend can at his office?

 

[Fuzznuts]

can you connect to any other servers on port 25? or is it just yours.

 

[Mark R]

When you say 'at home' do you mean on the LAN, or on a seperate network connected via the internet?

If the latter, then it is possible that your ISP blocks SMTP traffic (many do). You may need to configure your server to accept connections on an alternative port.

 

[Fuzznuts]

Originally posted by: Mark R
When you say 'at home' do you mean on the LAN, or on a seperate network connected via the internet?

If the latter, then it is possible that your ISP blocks SMTP traffic (many do). You may need to configure your server to accept connections on an alternative port.

thats just where i was heading

 

[suklee]

Originally posted by: Fuzznuts
can you connect to any other servers on port 25? or is it just yours.

It looks like I can't connect to any servers on port 25... although I can't verify this.

Anyway, I know Mdaemon accepts SMTP on 366, so I've enabled port forwarding to my mail server and I can telnet from home now.

Is it safe, then, to disable port 25 on my router?

 

[Fuzznuts]

you shouldnt move the mail server off the default port of 25. as this is the default port all mail transactions will be aimed for it from externale eg say you send a mail from hotmail.com. hotmails smtp server will try to connect to yours on port 25 if it cant then mail will of course fail.

so moving it is not a good idea. if this is not a live mail server and you are using it for testing then by all means change the port. if its live then god no!!!

i spose what you could do to get round this is make 2 port forwards one from wan:25 to lan:366 and one from wan:366 to lan:366 that way both will work for you and externals.

 

[suklee]

Thanks for the insights, very helpful as usual Fuzz

Should make it clear that this is indeed a live 'server', but most mail does not come thru via SMTP directly... we use DomainPOP to retrieve it off our ISP's POP server and parse addresses. This port 366 will be for our employees who want to access the mail server from home/work/travel etc. So perhaps, I can safely disable 25 for the time being until such a time when we get rid of our ISP and route everything directly thru a change in DNS settings.