Incomplete SMTPUTF8 implementation

[Hrnkas]

According to RFC 6531, SMTPUTF8 must be used with BODY=8BITMIME.

The thing is, the original code works perfectly with Gmail SMTP Server, but there is an issue with Office365 SMTP Server (smtp.office365.com), that UTF8 encoded subject "Auftragsbestätigung" gets wrapped into quotet word: Subject: =?iso-8859-1?Q?Auftragsbest=C3=A4tigung?=

This happens on the server. VMIME sends it as plaintext: Subject: Auftragsbestätigung

I tried changing it myself in SMTPCommand::MAIL, changing following code:

cmd << " SMTPUTF8";

to

cmd << " SMTPUTF8 BODY=8BITMIME";

This modification still does not work with Office365 SMTP Server. Any idea what needs to be done in order to address Office365 server properly?

Apparently, MailKit does it properly and works with smtp.office365.com. It sends BODY=8BITMIME after SMTPUTF8.