sa prior to lmtp delivery

[pnelson]

RH 9
cyrus 2.1.13
sasl 2.1.13
sendmail 8,12,8
spamassassin 2.44

Have been using sa on my clients (evolution) and then sending the INBOX
inbound mail to a filter that runs spamc -e to check for spam.  This
works great.  But I would like to move this to sendmail and then use
sieve to filter spam to my INBOX/zjunk mailbox.  The problem is I cant
figure out how.

How do you setup sendmail to first filter for spam and then send the
email onto cyrus lmtp for delivery, where sieve pprocesses the email
header for a spam line (or whatever sa does to the header).  Anyone give
me a clue, I'm kinda lost... and feeling like it can't be done.