[Mailman-Users] Trapping a post with a blank Subject:

[Hank van Cleef]

How can I catch a post sent to the list that has nothing in the
Subject: field?

It is the first post in a thread that I need to catch.  Mailman adds
(no subject) before distributing the post, and I can trap all the
responses.  But evidently that is added after the incoming post
headers are scanned.

I've tried several strings in the spam filter, but I don't get
reliable results.  I don't know what various MUA's actually put in
that field, but a simple \n seems to provoke a lot of false trapping
on Windows browsers that are actually sending subject line contents.

Hank