[Exim] Exim Comparsion

'ello gurus,

Background:

I'm currently advising a client (with a mail volume of around 100k mails
a day with growth potential to about a million/day) to look at solutions
which involves front end MTA solutions such as exim/postfix or even
"ugh" qmail. The mail backend is Sun JES iMS and I need to setup front
end mail servers which can do mail filtering (spamasssassin or
brightmail hooks, rbls, virus scanning with ClamAV and (i.e. more than
one) TM) and then use SunONE Directory Server LDAP to route mail to
backend mail host's by looking at the user's ldap attributes (including
optin for Virus/SPAM checking). The front end needs to be flexible and
secure. The client also would like to run this MTA chrooted. There
already is a clustered backend which does everything and the front end
mail cluster will take some of the overhead of away.

Question:

I'm looking for a front end solution which can do all of this. Surely
all three MTA's can LDAP and scale well except

#1) qmail hooks into SA/Amavisd-new/ClamAV/LDAP is a hacking approach
and whatever docs available on line deal with non-standard approach, not
much information about Directory Server, running two instances of qmail
etc.

#2) Postfix seems to all of this, is modular with a small memory
footprint and works nicely with Amavisd-new/LDAP and can run chrooted.
Except that Amavisd-new can't scale and I'm very apprehensive on setting
this up and having another point-of-failure to work on

#3) Exim can pretty much everything above and you don't need the extra
programs to maintain consistency. However, has anyone run exim chrooted
and/or gotten better performance (numbers would be nice) than postfix.

I would also like this solution to be simple enough (i.e.
packaging/deployment) to implement in case any of these frontends go
down. Any insights would be great.

Kind Regards,

-Kevin

--
Systems Engineer
Open-Systems Group