procmail as sendmail filter

Hello all,

Please excuse if this is not really the correct list for this, but I think
it is relevant to both procmail and sendmail.

I would like to create a filter on our mail relay that would bounce any mail
to sender that is going to certain domains based upon the size of the
message. This would have to be done in the sendmail rulesets somehow before
it gets routed to the correct delivery agent.

Any ideas on how I could configure this?

Thanks for any help,

Brian