RFC 5321 specifies that the body of an email be encoded as 7 bit, US-ASCII. The 8BITMIME extension allow the body to be encoded as 8 bit. An SMTP server can advertise that it supports 8BITMIME in its response to the
250-smtp.example.com at your service 250 8BITMIME
And the SMTP client can tell the server that it will use this extension in the
MAIL FROM: <firstname.lastname@example.org> BODY=8BITMIME
Most SMTP servers today support 8BITMIME and do so with UTF-8.
Question: Are there any SMTP servers or email clients that support 8BITMIME but do so by using an encoding other than UTF-8? If so, which ones and what encoding?