I wanted spamassassin to be called only when external mail arrives.
Here's what I used - after a lot of faffing around. From memory it
inspects the last From: header. It only scans for spam if the user
has set up a "Spam" folder also:
#/etc/procmailrc
RMIN = 1 # set to your Received count for local mail; may well be 1
WS = ' ' # a space and a tab inside the single-quotes
MYSERVER = mypc.mydomain.com # Substitute your mailserver here
:0
* $ 1^1 ^Received: from \/[^$WS]+
{
RCOUNT = $=
BOTTOMHOST = $MATCH
:0fw: spamassassin.lock
* $ $RCOUNT ^0
* $ -$RMIN ^0 MATCH ?? ^^$\MYSERVER^^
* < 256000
* ? test -d $HOME/.maildir/.Spam
| /usr/bin/spamc
}
