External port 25 blocked

I just realized that my linode is not accepting connecting on port 25. Locally, it works. I feel like i'm missing something obvious.

From the localhost:

telnet localhost 25


Connected to localhost.localdomain.

Escape character is '^]'.

220 lixxx-xxx.members.linode.com ESMTP Exim 4.72 Mon, 25 Jun 2012 20:39:51 -0400

netstat -plntu |grep :25

tcp 0 0* LISTEN 3091/exim4

tcp6 0 0 :::25 :::* LISTEN 3091/exim4

grep local_inter update-exim4.conf.conf


But from my mac:

telnet my_host 110

Trying xx.xxx.xx.xxx…

Connected to my_host

Escape character is '^]'.

telnet my_host 25

Trying xx.xxx.xx.xxx…

telnet: connect to address xx.xxx.xx.xxx: Operation timed out

Mailing to my_host (which forwards email to my gmail address), does not work.

Mailing to localhost does indeed forward properly.

This used to work, though. I'm assuming i made a change and forgot what it was. Please help me figure this out.

5 Replies

Are you sure your ISP isn't blocking port 25?

Have you made sure your ISP isn't blocking outbound port 25? You can test this by seeing if another mailserver is blocked on port 25. I know for a fact mail2.linode.com should accept connections on port 25. Won't allow you to send mail, but TCP handshake should complete.


Hmm.. good point.

telnet mail2.linode.com 25


telnet: connect to address Operation timed out

telnet: Unable to connect to remote host

OK, so that's a local issue. And should have been more obvious. Thanx.

Now to see why the email is not forwarding.

From the linode:

mail test@my_host

Subject: test




I receive the email on gmail as soon as i check. Sending it to that address from gmail itself fails. I noticed it just before as a website was emailing my forwarded address and i never received it.

Further testing. I setup a quick ubuntu on AWS (Amazon Web Services). Mailing from there works, and indeed i can telnet to port 25 on myhost.

I'm still trying want to figure out why i can't email it from gmail, and why another website sending me a confirmation email fails. Maybe i ought to try until tomorrow.


I receive the email on gmail as soon as i check. Sending it to that address from gmail itself fails.

Maybe I'm reading you wrong. But if your test is xyz@gmail.com -> linode, forwarding to -> xyz@gmail.com, you will never see the return email. Gmail does some black magic (deduplication, maybe?) that makes such bounced emails vanish into the ether.

Hmm, now I'm kind of curious if it's based on the existence of a copy of the mail in your Sent Items folder, or something else. I guess it could be tested by setting the forwarding server to delay the mail by a few minutes, and deleting the Sent Items copy in the meantime…


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