This feature has been rejected in the past.

Why would one want to use anything other than UTF-8 when writing messages?

@emersion For Latin languages, I agree that UTF-8 feels like it's a strictly better choice, and has almost universal adoption. Globally, there are some other encodings that have a decent amount of use (i.e. GB18030 for Chinese, Shift JIS & EUC-JP for Japanese, etc.). I agree that UTF-8 is equally a good choice for representing those languages, but I feel like the consumer of the library should be welcome to opt in to whatever charset they might want to use (or need to use, if integrating with a legacy system).

Again, I agree with you that UTF-8 is probably the best choice if I'm choosing to craft and send an email. My argument for this change is that we let the developer using the library make that choice, since we can't assume that UTF-8 always meets the needs of their project. (In particular, I am such a developer trying to support crafting emails of various charsets, which is not possible without this change)

That doesn't seem like a compelling explanation to me, sorry.

@emersion Could you elaborate on your rationale here? Any chance you could reconsider this?

For anyone who has a requirement to write emails in other charsets, which is common in many parts of the world, we're having to maintain a fork of this library.

There's already support for conversion in reading, why not also writing?

Sorry, no. I strongly believe that everyone should just use UTF-8. (Note, nobody forces you to use this library, and yeah feel free to fork.)

Thanks, I'm still having trouble understanding the reasoning here. Why is writing different from reading? If everyone should just use UTF-8, then why support reading other charsets?

There is a great deal of emails stored in files, databases and such with legacy encodings.

OK, and why not support writing in different charsets to better interoperate with the great deal of systems that use legacy encodings?

Systems can change, messages can't.

That's not really a meaningful difference when I don't control the third party system.