[Mimedefang] Blocking messages spoofed with my own e-maill address

[Stefano McGhee]

Hello Jeff,
	 
>  
> I have been seeing a lot of spam come in where the sender faked my own
> e-mail address as the sender's address.  I should never be receiving a
> message from outside my network from my domain, so I would think it
> would be easy to make a MIMEDefang filter to block these.  My Perl
> skills are woefully lacking, and I am sure others must have had this
> problem.  Anybody care to share their filter rules to block 
> this kind of
> spam?

Don't like Perl?  Put this in your Sendmail access DB file and you won't
need Perl.

From:yourdomain.com                 ERROR:"550 No local relay"

You'll need to make sure your sendmail.mc/cf has the option to allow
blacklists.  This prevents people from outside trying to send you mail with
your domain.  HOWEVER, beware that some "legitimate" websites like to send
you confirmation messages or news messages from your own account, so they
will be blocked.  I'm OK with it because I think it's wrong, but that's
just me.

Write back if you need more clarafication...

Cheers,

Stefano