The sender Application Entity composes an email and sends that email using a standard email transmission protocol.
The sender shall compose an email in compliance with RFCs 2045 and 2046, as a MIME Encoded email. RFC 2046 defines both MIME encoding and the mechanisms to be used for breaking up the email message if it is too large for the email system to send as a single email. The sender may request delivery acknowledgement and problem notification in accordance with RFCs 3464 and 3798, but shall be prepared for email recipients that do not implement RFCs 3464 and 3798. The sender shall send the email by means of Simple Mail Transfer Protocol (RFC 2821).
Note: The sender Application Entity does not need to be a single software program. For example, the attachment file may be created independently and then a generic email program used to manage attaching the file and sending the email.