Support X-MSYS-API header #27
Description
Please add support for the X-MSYS-API header documented here.
As far as I can tell, this is the only way to create a true Bcc email (with Bcc header). Using the Nodemailer bcc field does send an email to the Bcc recipients but it does not include the Bcc header (which is important for distinguishing an email as being sent as Bcc).