If you qmail-smtpd under tcpserver, the following will update relay allow and relay forbid rules.

Create a file called /etc/tcp.smtp and put in it:

127.:allow,RELAYCLIENT=""
1.1.1.1:allow,RELAYCLIENT=""
2.2.:allow,RELAYCLIENT=""
2.2.2.5:deny

Qmail uses simple pattern matching so only classful subnets are allowed. Sorry, no CIDR notation.

The example above will allow/deny:

• Allow relaying from 127.* your localhost subnet of 127.0.0.0/8
• Allow the /32 address of 1.1.1.1
• Allow 2.2.* the /16 subnet of 2.2.0.0/16
• Specifically forbid 2.2.2.5

In order to implement these rules you need to update the server tcp.smpt.cbd file and restart Qmail.

First, back up /etc/tcp.smtp, then run the command:
tcprules /etc/tcp.smtp.cdb /etc/tcp.smtp.tmp < /etc/tcp.smtp

If the rules don’t update, make sure -x /etc/tcp.smtp.cdb is after tcpserver in your start script, then restart Qmail.

Did you find this post useful or have questions or comments?  Please let me know!

Qmail does not allow you to restrict max recipients or max messages per session. I saw reference to a plugin to handle these controls, but do not know the name of it.

You can restrict max message size in /va/qmail/control/databytes

Example:

$ cat /var/qmail/control/databytes
10485760

That’s a 10MB limit

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Example:

example1.com:10.0.0.1
example1.com:10.0.0.2

Will send mail only to 10.0.0.1 The second entry will be ignored.

You are better off using round-robin DNS or submitting a patch to handle priority routing.

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