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. Steve ------------------------------------------------------ Mailman-Users mailing list Mailman-Users@python.org https://mail.python.org/mailman/listinfo/mailman-users Mailman FAQ: http://wiki.list.org/x/AgA3 Security Policy: http://wiki.list.org/x/QIA9 Searchable Archives: http://www.mail-archive.com/mailman-users%40python.org/ Unsubscribe: https://mail.python.org/mailman/options/mailman-users/archive%40jab.org
