However, it is too restrictive to a particular need where the same result can be achieved with a simple SUBJECT line. The SUBJECT line idea can address this and many other neat concepts such as overhead reducing mail driven events. For example, subcribing to a mail list:
EHLO mailer.foobar.com MAIL FROM: <jsmoe@xxxxxxxxxxx> RCPT TO: listadmin-somelist@xxxxxxxxxxxxx SUBJECT: subscribe QUIT
The feature and product benefits offered by a SUBJECT line design change is much greater and wider than this specific EHLO/MAIL FROM design change which targets only one concept.