Hi,

1) I am attempting to implement a solution wherein I have a whitelist of senders
whose mails go to the inbox (nothing new here). I don't know for sure yet, but
I think it'd not be too hard to make maildrop work with my whitelist (?). (I
know I can use whitelisting in SpamAssassin, for example, but what I am trying
to do (see below) isn't necessarily related to spam scanning. So I figure the
best placement for this is in the delivery agent. Am I wrong?)

2) The kicker is that I want all other (non-whitelisted senders) mail to be
filtered elsewhere. I think if I can come up with a maildrop script that
accomplishes #1 above, this may not be too hard, but I am concerned about two
things:

a) Reading in a (possibly big) whitelist from a file or database during
maildrop execution may not be efficient(?) and may be hard to code in maildrop
script language

b) The FROM header is easily forged -- can I rely on typical postfix EHLO and
client checks (such as requiring the client domain to match the sender domain or
whatever) to catch those forgeries and safely be naive/trusting of what the FROM
header says if I implement this in maildrop? Even if this kind of filtering was
implemented elsewhere, it'd still have to be based on the FROM header, so maybe
this question becomes irrelevant except to know how much postfix rules can help
make the FROM header trustable....??

I'd very much appreciate feedback!