input: [Token] XEXCH50 [Type] Verb [Reference] Microsoft [SMTP server] Microsoft Exchange Server [Comments] 
output: Allows transfer of binary data with Exchange specific recipient information (eg plain text only versus MIME, etc). If accepted, receiver SMTP servers sends 354 Send Binary data and sending SMTP server sends the number of bytes as the first parameter on the XEXCH50 command. Once these bytes are sent, the receiving SMTP server sends an acknowledgement