no, it's not legal. the biggest problem I see is that the text/plain
body part is not well-formed - even if it is going to be blank there
needs to be two blank lines between the content-type field and the
boundary marker for the next body part.
also, the reporting MTA should be a fully-qualified domain name;
the received-from-mta type field should be "dns" presumably (not "dsn")
and that name should also be fully qualified. finally use of the "dns"
type for an IP address literal in Remote-MTA seems a bit suspect though
I confess that the standards don't say what to do with this case.
but it's the first problem that would most likely keep the DSN from