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

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".

They're both optional, but one comes attached to a big warning message.

Well… yes… no… SHOULD means that you must either do the thing or understand the consequences of not doing it. That's not simply optional, the two options are to ① spend time on writing code and ② spend time on learning the consequences. Either way you need to think hard and spend time. And that's why the definition of SHOULD includes the word "must".

> So should is optional, people!

Only once you have satisfied:

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

In other words, you better have a damn good reason for deciding not to do it.

And (possibly even more to the point), you must decide not to do it, rather than simply throwing code at the wall until most emails make it through unscathed.

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.