Sendmail/Port 25 on host24

Most distributions these days configure the MTA to only listen to the loopback interface (127.0.0.1) by default. If you're running Sendmail on Fedora Core, you will want to comment out ("dnl") the line in /etc/mail/sendmail.mc that says:

DAEMON_OPTIONS(`Port=smtp,Addr=127.0.0.1, Name=MTA')dnl

After editing sendmail.mc you should cd to /etc/mail and run make to rebuild sendmail.cf, and then use service sendmail restart or /etc/init.d/sendmail restart to restart sendmail.

Note: if you are going to use your system as an outbound mail server, you should enable TLS and SMTP AUTH on ports 587 and/or 465. You don't want to run an open relay.

I am using pop-before-smtp and it workes like a dream…

@xiopher:

I am using pop-before-smtp and it workes like a dream…
Be aware that this isn't secure with vanilla POP. POP authenticates in the clear, so your username and password are easily sniffed. If that happens, not only is your mail compromised, but also your server can relay spam. It's better than an open relay but is still vulnerable.