proxy firewall and email

[Neil Ratzlaff <neil.ratzlaff () ucop edu>]

Caveat:  I can give advice to the site in question, but I have no control 
over it.  The site admins are not very knowledgable about either their mail 
server or firewall and consultants set it up for them.

I have a question about Raptor firewall and MS Exchange smtp server behind 
it.  The information below is to the best of my knowledge, but be aware I 
know nothing about either Raptor or Exchange or NT.   Together they seem to 
create an open relay for spam.

The Raptor firewall accepts all mail and passes it to the smtp server for 
delivery.  If the recipient is not a valid user, the mail gets bounced by 
the smtp server, but to the address in the From field, not to the sender or 
last smtp server.  Since you can put anything you want to in that field, 
you can send spam via this relay, albeit perhaps slowly.  The firewall does 
not keep a list of legitimate users, so it  can't reject mail as it should.

I am sure other places have dealt with this process, so how can I advise 
this site to fix their setup?  I would expect that Raptor should be able to 
hook into Exchange to validate recipients, but the site admin tells me it 
can't.  I would be happy to tell them how to make Raptor just check that 
the recipient domain is correct, which should be easy to check.  A post 
from the May99 archive of this list strongly suggests this is the correct 
way to proceed.

Can anyone tell me how to explain to the site how to make this work?

Thanks,
Neil