Pointers to resource materials for Postfix?

[David Wolfskill]

I need to do a couple of things with some Postfix installations; I'm
looking for pointers to resources that others have found useful.  I have
a copy of the O'Reilly book by Kyle D. Dent, but I'm finding it
insufficient.  (I confess that I'm a little disappointed in the book:
it's dated 2004, but appears to be a bit out-dated in some respects.)

The first of these -- perhaps the more urgent of the two -- is to
address performance:  I need to understand how the various "knobs" Postfix
supplies interact, and where I can get the most "bang for the buck."

The second is in some conflict with the first: I need to understand what
would be involved in setting up a Postfix MTA to (e.g.) reject unwanted
mail during the SMTP conversation, but to have the criteria for doing
that vary from one recipient to another -- even if the different
recipients are recipients of the same message.  Oh -- and I'll have
multiple MXen that need to maintain a consistent set of criteria.

I'd appreciate useful pointers; I plan to summarize responses.

Thanks!

Peace,
david
-- 
David H. Wolfskill				david at catwhisker.org
Mail filters, like sewers, need to be most restrictive at the point of entry.

See http://www.catwhisker.org/~david/publickey.gpg for my public key.