[Mimedefang] Block emails pretending to come from my domain

[Michael Sims]

Mark Penkower wrote:
> 1 - Is there a way to block all emails coming from outside of
> roycenet.com, including
>       people forging the email addresses of legitimate users who send
>       emails to our domain from outside of the organization, but at
> the same time allowing
>       the legitimate users to send emails to the organization?

Yes, implement SMTP AUTH on the MTA that your internal users use to relay,
and force your users on other networks to relay through your server via SMTP
AUTH.  That's easier said than done though.

> 2 - If that is not possible, can I block all people forging the email
> addresses of
>        legitimate users who send emails from outside of the
> organization, but keep
>        a safe list of people who don't get blocked?

Yes, use filter_sender().  Inside the filter_sender() sub define an array of
email addresses that will serve as your whitelist.  Check the IP of the
relay, and if it isn't in your network AND the sender address isn't in your
whitelist array, then reject or discard the message...

HTH

___________________________________________
Michael Sims
Project Analyst - Information Technology
Crye-Leike Realtors
Office: (901)758-5648  Pager: (901)769-3722
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