> SHOULD is a requirement.

I once had a job where reading standards documents was my bread and butter.

SHOULD is not a requirement. It is a recommendation. For requirements they use SHALL.

My team was writing code that was safety related. Bad bugs could mean lives lost. We happily ignored a lot of SHOULDs and were open about it. We did it not because we had a good reason, but because it was convenient. We never justified it. Before our code could be released, everything was audited by a 3rd party auditor.

It's totally fine to ignore SHOULD.

▲ calvinmorrison an hour ago | parent | next [-]

Email is about standards like browsers were about standards in 2017...

▲ seb1204 3 hours ago | parent | prev | next [-]

Yes, except there seems to be a move on the best words from SHALL to MUST and from SHOULD to MAY. IANAL but I recall reading this in e.g. legal language guidance sites.

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aunderscored 2 hours ago | parent [-]

RFC language is expmicltly defined in 2119[0]. Any other interpretation is incorrect.

[0] https://www.rfc-editor.org/rfc/rfc2119

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Alive-in-2025 2 hours ago | parent [-]

Thank you for that. So should is optional, people!

	▲	strken 33 minutes ago \| parent \| next [-]
		Pulling exact quotes out, SHOULD means "there may exist valid reasons in particular circumstances to ignore a particular item" while MAY means "an item is truly optional." I don't think this can be interpreted as simply "should is optional".
	▲	sisve an hour ago \| parent \| prev [-]
		I think that is a bit to easy. MAY is described ar optional. SHOULD - Should really be there. It's not MUST, you can ignore it but do not come crying if your email is not delivered to some of your customers ! you should have though about that before.

▲ dsl 2 hours ago | parent | prev [-]

Maybe the standards documents you are used to differ from RFCs, but here is the official language:

   3. SHOULD   This word, or the adjective "RECOMMENDED", mean that there
      may exist valid reasons in particular circumstances to ignore a
      particular item, but the full implications must be understood and
      carefully weighed before choosing a different course.

SHOULD is effectively REQUIRED unless it conflicts with another standards requirement or you have a very specific edge case.

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jcelerier an hour ago | parent | next [-]

I just don't understand how you get from the text you pasted to "required". Nowhere does it say that anything is effectively required. Words have meaning.

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zdragnar an hour ago | parent [-]

> the full implications must be understood and carefully weighed before choosing a different course.

Note the use of the word "must" used twice there. Barring a sufficiently good reason and accepting the consequences, this becomes a very poorly worded "required".

The spec would have been far better starting with SHALL and then carving out the allowance for exceptions.

	▲	shakna an hour ago \| parent \| next [-]
		No, its not a "required"... It means someone may have reasons not to use something, and so spec implementors need to allow for circumstances where it is not present. Those reasons can be anything. Legal, practical, technological, ideaological. You don't know. All you know is not using it is explicitly permitted.
	▲	WJW 36 minutes ago \| parent \| prev [-]
		I don't even know how you got to "used twice" tbh. Both your own comment AND the post you quoted from only have a single "must". The only thing that text demands is understanding and carefully weighing the implications. If, having done that, you conclude that you don't want to then there is absolutely nothing in the spec stopping you. Maybe the spec would have been better off putting more stuff in SHALL and less in SHOULD, but as written that is definitely not the case.

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andoando 3 minutes ago | parent | prev | next [-]

required means it must exist, not that it may or may not exist depending on the reason

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BeetleB 43 minutes ago | parent | prev [-]

Nope, it's exactly what it says: RECOMMENDED.

Any time any document (standards or otherwise) says something is recommended, then of course you should think it through before going against the recommendation. Going from their verbiage to:

> SHOULD is effectively REQUIRED unless it conflicts with another standards requirement or you have a very specific edge case.

is a fairly big leap.