A 'Whitelist / Blacklist tool': This is an
excellent method for fine-grain tuning your MTA access *or* you can rely completely
on this method for access control in most MTAs, certainly in Postfix and Sendmail.
Your MTA must be compiled *--with-XXsql* and configured to use MySQL or PostgreSQL.
If you already use MTA Domains for your destination addresses and or mail transport,
the appropriate tables for this feature exist.
If not, please read help and learn how to do this from the configuration window.
With this tool, you create the 'sender' / 'action' directive for the MTA.
Please read MTA HELP