The stream must contain data in MIME format, other formats are not supported. MIME files often have the '.eml' extension and are produced by Outlook Express. In contrast, Outlook produces '.msg' files that are not MIME files and therefore cannot be sent using this method.
If the sender address argument is null (Nothing in Visual Basic), it is taken from the from the "Sender" header field
or from the first address in the "From" field if the "Sender" is missing.
If the sender address argument is empty string, it means null sender - same behavior as if "<>" would be specified.
If the recipients argument is null (Nothing in Visual Basic), it overrides the list of recipients contained in the message. If the recipients argument is null, the list of recipients is extracted from "To", "Cc" and "Bcc" header fields.
The "Bcc" field is removed from message headers prior to sending.
Set the AllowNullSender property to allow sending a mail without a sender specified.