CB

Currently PHPMailer defaults to 8bit encoding, which if UTF-8 is present will fallback to quoted-printable. This breaks UTF-8 emails on hotmail. Setting encoding to base64 works around this issue. A parameter to select the encoding would be useful or potentially dynamically changing the encoding if the email is being sent to hotmail and is UTF-8.

First #8140 should be applied so we're using latest PHPMailer.