- some list expanders used it as a loop-prevention flag - assuming
that any message that had precedence: bulk had already been
fowarded to the list.
- one mail gateway used precedence for 'priority' and would bounce
any message that contained a precedence keyword that it did not
understand. IIRC "bulk" was one of those not understood.
Neither of those count as harmful.
so having people unable to receive IETF mail because of your naivete
p.s. perhaps you should see if Microsoft is hiring. it sounds like you'd
fit right in :)