but I do understand that, currently, setting precedence is probably the
most effective way to get 'bots to not respond to your message.
Well, what are the specific problems with the precedence? Often knowing
the problem better leads to finding a solution.
Precedence has been overloaded for so many different things that occasionally
they've actually conflicted with one another - so assertion of a Precedence
field could cause your mail to bounce or fail to be delivered.
things Precedence has been used for:
queueing priority in sendmail
whether to return content in nondelivery reports
"do not respond" flag for vacation
flag used to prevent loops among peered mailing lists
(the assumption here was that Precedence is only set by lists,
so if a mesage arrives at a list with Precedence set, it must
have been forwarded back to the list by a subscriber of some
list or another - so don't forward it back to the list because
that might create a loop)
indication of message priority gatewayed to/from other mail systems
(one gateway would not forward a message if it didn't like the
precedence value - fortunately this one is probably extinct)
and probably a few more that I don't recall at the moment.
You're missing at least two:
whether or not to return delayed nondelivery reports
indication of message importance (in the X.400 sense)
The other problem is that the values used to get the various functions