I subscribe to several mailing lists that are gated to Usenet. As you
know, the "References: " header cites the message IDs of earlier articles
the poster is quoting. This allows newsreaders like trn to present news
articles to the user with true threading.
As a courtesy to other Usenet readers, when I post a followup article
through the mail-to-news gateway, I manually add "References: " message IDs.
However, when I see my article propogated through Usenet or the mailing
list, the header has been stripped. trn has no way to properly thread the
Is this a "feature"? The mailing lists are managed on ListProc, ListServ,
and Majordomo. I assume this happens at the MLM level, since I don't see
the header on messages from the list. I don't know how the gateway is
managed; I suppose it could happen at that level.
I have yet to come across a MUA that threads e-mail messages. The
"In-Reply-To: " header, where it exists, could be used to thread.
My MUA, pine, adds this header to my replies. However, some MLMs delete
it. I have noticed that this header is preserved with Majordomo, but is not
passed through by ListProc.
Is either header mandatory, either within Usenet or mail? Are there
mandatory rules on the use of gateways, such that headers needed by one
side are supplied by the other? Could an "In-Reply-To: " header be
converted to a "References: " header, or vice versa?
Is an "In-Reply-To: " header allowed to cite more than one message ID?