swaks is fantastic PERL script: you can do things like
swaks -t jsmith@uk.company.com -s mailserver -q RCPT -f jsmith@uk.company.com
…and it logs the IO on screen.
There is a changelog for it here.
Setting up Spam Assassin with qmail
Rather than using the qmail-queue patch and qmail-scanner to get Spam Assassin working with qmail this page suggests replacing qmail-queue with a simple sh script.
Seems to work on our internal work server, but of course you would need to put qmail-scanner in to check for viri.
