postfix and mailing the same e-mail to hundreds of clients

[Razvan Chitu]

Hello there,
    The question here is a fairly simple one: given a simple postfix 
mail server (primary mx), with local *nix user accounts, I want to know 
the best way of implementing the following situation:
    - Someone (a.k.a. the management) sends an e-mail with attachments 
to a certain e-mail address on this server from the internal network 
(let's say service_clie...@mydomain.com) and they
want this e-mail relayed to some hundred (less than a thousand) e-mail 
addresses. Same thing for fsma_clie...@mydomain.com a.s.o. (in fact a 
mailing list). I could use the alias file for this
purpose, the big disadvantage is that it's hard to maintain (the 
managers wants to be able to maintain the alias / mailing list by 
themselves, so I was thinking a web interface like the postfixadmin's
without a MySQL database). I don't want however everybody over the 
Internet to be able to send e-mails to these addresses 
(service_clie...@mydomain.com, etc), that would be a huge spam
source and spam is what I want least. Maybe the question kind of 
"nooby", however I look forward to your replies and suggestions (or the 
rtfm's as long as you provide a link to the manual :))

Kind regards,
/C.R.