[comp.protocols.tcp-ip] mx-existence and header etiquette

ROODE@BIONET-20.ARPA (David Roode) (05/13/87)

Phase-in timetables for defacto standards are generally informal.
What's the feeling about the use of host names that are only valid
where there is support for both a host name resolver and MX name
server domain entries?  It seems reasonable for forwarding hosts to
show up in the From: header as a courtesy to those hosts who do not
yet support MX-existence.  Is this support a "required" or an
"optional" part of name resolvers?  At least considering that on some
of the networks composing the internet name server use is optional,
some period of visibilty for forwarding makes sense.

Apparently RELAY.CS.NET does follow this principle, but
not all the hosts relaying UUCP hosts' mail to the Internet
do.
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