Russ Allbery wrote:
message/delivery-status isn't always applicable as the second part.
No, but a message/generic-notification can be.
Which portion? Everything the average user should need to know ought to
be clearly explained in the text/plain leader.
If everything that's important is in the text/plain section, why on earth
should one send anything other than that?
Because humans aren't the only ones that get them.
Eric A. Hall http://www.ehsco.com/
Internet Core Protocols http://www.oreilly.com/catalog/coreprot/