[Mimedefang] validating 'possibly forged' helo IP's?

[WBrown at e1b.org]

> Try adding 150 PTR records for a given IP address and watch all hell
> break loose. :-)
> 
> (The large reply will make the DNS server want to fall back to TCP,
> which is blocked by a lot of firewalls whose admins forget (if they
> ever knew) that DNS can run over TCP as well as UDP.)

Wearing the DNS hat as well as mail, I made damn sure that the firewalls 
allowed 53 TCP and UDP.  I would think that if they are blocking TCP, they 
would have been seeing some odd behavior already.