There is a question I think the community of unix.SE would be able to provide an answer to, and which is related to the Simple Mail Transfer Protocol and seeks information about some historic background (i.e. "what was the technical background/reason that caused tha 7bit encoding limitation")

Even though I have seen both tags smtp and history used for questions that related to the question I feel unsure if this is an permitted on topic question.

I expect the question to be answerable with reference to some limitations with regards to stop characters and transmission channels used during the time SMTP was used. With that respect the question would imho not be opinion based, but might have some factual background, I am simply not aware of and could not find adequate information yet, hence the desire to ask it.

It would be great also, to receive an information if there is a different SE community that would be more related to the question. Yet I think that a big percentag of MTA systems are rooted in the unix/linux world.


Protocols tend to fall between the gaps between Stack Exchange sites.

  • Super User and Server Fault are fine for questions about configuring software to support a protocol, but questions about the protocol itself are usually off-topic.
  • Unix & Linux accepts architecture questions that SU and SF would reject. Questions about protocols fit under this umbrella, but the protocol has to have strong ties to Unix, and the question has to stay closer to user-level than programmer-level.
  • Stack Overflow is fine for questions about writing software to support a protocol, but questions about the protocol itself are usually off-topic.
  • Software Engineering might be ok for questions about designing a new protocol, but I don't think protocol history would fare well there.
  • Electrical Engineering is a fine place for questions about protocols at the electrical level, but not much above.
  • Engineering pretty much excludes software engineering.
  • Network Engineering does accept questions about network protocols, but they have to be sufficiently advanced: NE is for professionals, or at least people who can talk to professionals on an equal basis.
  • Cryptography and Security are good places to ask about the cryptography and security aspects of a protocol, but not for other aspects.
  • The more theoretical aspects of how to design a protocol are on-topic on Computer Science, but concrete questions about a specific protocols are right out.
  • Retrocomputing is a fine place for questions about a (version of a) protocol that's no longer used in production (or only on some rare legacy systems), but not for anything that's still industrially relevant.

In your case, I think Retrocomputing would be the best place. NE might be a contender for current versions of a protocol, but not for history. U&L would be ok if the answer was likely to reference Unix systems, but in this case I suspect it doesn't.

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