I'm trying to cleanup all the crap that comes into my mailing list owner mailboxes, and I'm now just down to wanting to automagically bin all *-subscribe requests with a non-blank Subject header. These are invariably spammers who've found a link to a mailbox via our website subscribe portlets/forms.

While I could write a filter to do this and place it ahead of the couriermlm msg in the maildrop recipe, it occurs to me that to write a performant C program, it would have somewhat similar functionality to couriermlm.