SENDMAIL: Listening to multiple SMTP ports on a single mail server instance

Frederick Denny (
v. 0.90.04 14th of Nov 2006

Background: As the world becomes more conscious simple tasks like dropping an outgoing e-mail on SMTP port 25 so do hackers and IT Managers.
Many times IT groups do such things as block ports using local PC firewalls and Anti-virus solutions that try to stop trojan mail bombs etc..
In my case the corporate IT groups installed McAfee Enterprise 8 on our general use PC's which stopped our local application from sending mail.

Note: For initial configuration of Sendmail 8.10.x and higher see: How to setup an E-Mail Relay Host with Sendmail (if you are setting up a relayed mailhost)

Scenario  (Creating a mail server that listens to SMTP ports 25 and 580):
Basically you add an option line to your file. The option is called "
This option that came out in Sendmail 8.10, it let's sendmail listen on multiple ports without having to run a separate sendmail instance for each port.
When the
DaemonPortOptions is put in your (or added it to your master, the sendmail daemon listens on the ports specified.
i.e. And exact line

O DaemonPortOptions=Name=MSA
O DaemonPortOptions=Name=FredMail, Addr=, Port=580, Modifiers=bh

Configuration options:
DaemonPortOptions=Name=name, Modifiers=modifiers, Family=family, Address=addr, Port=port, Listen=listen, SndBufSize=size, RcvBufSizesize
 The example below shows the lines required to modify your master so you can have a good template for your mail server.
Remember to recompile you if you modify it:  m4 > /etc/ 

When you are done making your changes do not forget to restart your mail server:

 /etc/mail/sendmail stop
 /etc/mail/sendmail start