[Mimedefang] SA-score multi-recipient mail before breaking up?

[Jim O'Leary]

We've been using mimedefang/spamassassin for a couple of years now with 
mostly good results.  The one problem we do run into is on the break-up and 
re-submission of multi-recipient emails to the submit queue, where 
clientmqueue backlogs become unwieldy when the machines are too busy to 
accept on port 25.

We have an idea we hope can reduce the load significantly.  We'd like to 
perform a spamassassin scan on multi-recipient messages *before* breaking 
them up.  If the score exceeds a certain threshold we want to reject it 
right up front - regardless of any individual user preferences, including 
whitelists.  Plus, if we do keep decide to keep it, a "basic" score might 
be inserted into the headers and we might use that to bypass or cut short 
the individual SA scans further down the pipeline.

Has anyone done anything similar to this?  We haven't done a whole lot of 
mimedefang customization, so we're looking for some direction on whether 
and how this could be done via mimedefang callbacks.