6) Message/Partial send over an 8 bit or binary path cannot be
converted in a MIME aware gateway from 8 bits to 7 bits due to the
prohibition on encoding of the message content type and the unknown
nature of the content
[...]
Alternate Solution2: Make an exception to the nested encoding rules for
message/partial.
Similar to alternate solution 2:
I'd prefer that the "no nested encoding" rule apply only to multipart/* and
message/rfc822. It's not clear that it makes sense to place constraints on
the encoding of other message/* types. For example, were a message/x400
content-type defined, it probably needs to be encoded in base64.
At any rate, I don't think the "no encoding" rule should apply to
message/partial.
Keith