Basically message-id munging for all messages.
better as an option? This helps with threading in usenet gating, as
what happens is this:
someone sends a mail with message-
gating replaces the message-id with
list member replies via mail,
"in-reply-to" header is set to the firstname.lastname@example.org
now when the
message is gated it can't thread because in-reply-to: (which is
translated into references:) is wrong.
Solution is to munge
all message-ids. Doesn't really do any harm AFAICT.