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Community ▶ Questions ▶ SMTP works only inside the box
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SMTP works only inside the box

email

Hello, everyone!

I just set up a sendmail in my CentOS 5.3 linux box.

And I am having problem accessing SMTP from the outside network.

When I try to telnet to SMTP inside linux console, it's okay.

Basically I used the same command in the Linux console and Windows Command Prompt.

telnet mail.example.com 25

I can ping to the mail.example.com so it's not DNS or ip problem.

I used iptables command to see if I set up firewalls but i didn't.

iptables -L

Any clues?

5 Replies

I'd run….

service iptables stop

just to make sure.

Can you connect to other port 25s? Many (most?) ISPs block outgoing traffic to port 25 to cut down on outgoing spam from hijacked computers.

Try:

telnet mail.hoopycat.com 25

I know that one's up and reachable. :-)

hoopycat

You are right!!

I tried your code and it didn't work. I guess I need to use ISP's SMTP.

There are some other options. You could use an SSH tunnel. Or you could use the submission port (587 I believe).

@Xan:

There are some other options. You could use an SSH tunnel. Or you could use the submission port (587 I believe).
Yeah, I've used 587 ever since Verizon started blocking 25.

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