Mail notification and UTF-8 "Title"

[maxatome]

If an email notification is created with a Title containing UTF-8 chars, like:

[release 🚀] {{.git.message}}

the encoding is not declared in the Subject header, so the mail reader can not render it correctly:

[release 🚀] …

To avoid doing it by ourselves:

=?UTF-8?Q?[release =f0=9f=9a=80]?= {{.git.message}}

Shouldn't the mail subject be automatically encoded using RFC 2047 if an UTF-8 character is detected?

[yesnault]

reopened
cf. #5464 (review)

on Thunderbird: