How to open sendmail receiving port

Question

I am trying to open port 25 for receiving mails from outside my server using sendmail. I want to read my mails with alpine and I don't need anything else. I have tried this:

firewall-cmd --zone=public --add-port=25/tcp

connection is accepted by this command

telnet 127.0.0.1 25

but it is refused by this

telnet mydomain.com 25

How can I open this port for outside connections?

But it gives me connection refused. I cant find the problem. — Az Az, Feb 05 '17 at 07:21
I solved the problem. sendmail was refusing connection. not firewall. I found a tutorial and configured sendmail. — Az Az, Feb 05 '17 at 11:17

score 1 · Accepted Answer · edited Jun 21 '17 at 02:01

Edit: updated link (proofpoint have taken over sendmail)

Sendmail FAQ 4.22 : Why can't I receive external mail?

Several vendors have changed the way that sendmail is run. They decided that most people need a client-only version of sendmail. So it is listening only on the localhost interface. Check the system documentation on how to change your .mc file [...]

netstat command may be used to check if sendmail is listening only on the localhost interface (127.0.0.1 or ::1). It is netstat -ant | grep :25 on Debian Linux.

How to open sendmail receiving port

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