[Mailman-Users] Message-ID required
Stephen J. Turnbull
turnbull.stephen.fw at u.tsukuba.ac.jp
Tue Feb 6 05:05:28 EST 2018
Mark Sapiro writes:
> On 02/05/2018 12:22 AM, Stephen J. Turnbull wrote:
> > According to RFC, Message-ID is an originator field, and MUST be
> > present and MUST be unique.
> Do you have a reference for this? I thought this was correct, but I
> recently looked it up in RFC 5322 and predecessors and those RFCs
> at least say it's optional and SHOULD be present.
You're right. I knew that it was SHOULD in RFC 822, but I thought
this was updated in RFC 1123 "Host Requirements" or maybe RFC 5598
"Email Architecture". I was wrong.
In any case, SHOULD is pretty close to MUST, especially in this case.
(What reasons based on interoperability issues can you think of for
omitting Message-ID? SHOULD means you need one!)
I'm guessing that since the RFC authors have deprecated use of
Message-ID for anything related to security, and its semantics are a
judgment call in any case, it's simply not reliable enough to promote
to MUST. So they never did.
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