validrcptto

The validrcptto patch consults a CDB file, /var/qmail/control/validrcptto.cdb which should contain every valid email address and alias on your server. Rather than generate this list manually or try to create our own script to do it, we'll utilize John Simpson's mkvalidrcptto script.
We've already installed djb's CDB program, so we can proceed with installing the CDB_File Perl module. If you've never used the CPAN shell before on this server, you'll need to configure it the default options it provides should be adequate.

In case the Perl module didn't install with the correct permissions, we'll use John Simpson's pfix script to fix them.

Installing the mkvalidrcptto script is simple matter of downloading it:

To create the initial CDB files, run mkvalidrcptto and mkauth commands with the -c option:

SMTP run script
The run script for your SMTP service might need to be modified to enable validrcptto checks. Uncomment:

Excluding addresses from validrcptto
In order to exclude some email addresses from the validrcptto file and not accept delivery to them, they can be added to /usr/local/bin/mkvalidrcptto by editing this section: