UTf7 supports about encoding

[hsivonen]

I think this should be closed as "won't fix", because this is a Web-oriented spec and not an email-oriented spec.

It does follow that if you are implementing an email client that performs MIME decoding in JavaScript running on a browser engine, you have to implement an UTF-7 decoder in JS instead of calling into a browser-provided facility like TextDecoder. That's somewhat unfortunate, but the alternative would be speccing UTF-7 as a special encoding that's exposed only via TextDecoder and not in other places where the Web Platform exposes decoder.

But then, JS email app developers need to implement the IMAP variant of UTF-7 in JS anyway. (Unless you are arguing that the spec should support that encoding, too, and even on the TextEncoder side.)

[annevk]

Agreed. If this becomes a big problem we can reconsider, but implementing your own special purpose encoding support in JavaScript is not that hard.