Ok - I have a pretty crazy one here ....  

I have a system  that for reasons too lengthy to get into here, needs
to send mail to a very bogus email address - something like <blah
blah>@realbogus.dl

I need the SMTP server to accept such mail for the realbogus.dl
domain, and then based on address (the <blah blah> part), send it to
the real recipient.

As a test I got exchange to do this by doing the following:


Tell exchange to accept domain realbogus.dl
Tell exchange to accept mail from the server that is sending it this mail 
make a new MailBox for each bogus email address <blah blah1>@realbogus.dl .. etc
make a custom recipient of type "internet email address" - for each
real recipient address.
Go into each new Mailbox and set the delivery options to an
alternate recipient which is the appropriate custom recipient mail
address.


I'd like to offer an alternate solution with Linux - just a smtp
server running on a small box who's only job is to do this little
translation and pass the mail along.  something fast to set up and
easy enough for a monkey to add more "email translations".....