Hm. The idea of a DSN being influenced by body-part headers is
architecturally inelegant, but it (sadly) makes a fair amount of sense when
dealing with gateways.
The case where a DSN is appropriate is the case of a content-converting
gateway; after delivery, an MDN is the only reasonable thing to do.
The text saying so might be clearer.
This extension does not guarantee any notification, of course; this should
be noted explicitly.
The specification should say exactly what values to put into the MDN or DSN
when generating one for this reason; 5.6.1 "Media not supported" seems
appropriate, or 5.6.3 "Conversion required but not supported", or you might
want to exercise the process for adding new status codes. See RFC 1893.
I don't have any advice for the MDN generation, but the doc should have.
Apart from these points of incompleteness, I think it makes a reasonable
amount of sense.
Have fun!
Harald
--
Harald Tveit Alvestrand, alvestrand(_at_)cisco(_dot_)com
+47 41 44 29 94
Personal email: Harald(_at_)Alvestrand(_dot_)no