🚀 go-pugleaf

   As far as who contains what routing information, all that is up to the
implimentor. The important thing is that the mail gets to the recipient.
For an ADMD MTA, all it needs to do is get mail to some MTA of the PRMD
that the recipient belongs to. For an MTA of a PRMD, all that's important is
that it is able to somehow route the mail to the MTA that services the UA of
the recipient.
  The knowledge of routing info is up to the implimentor of the ADMD or PRMD.
A PRMD MTA may have complete info of exactly who is where for the entire PRMD.
Or it may route by Organisational info to the right MTA within the PRMD. Or
it may route everything that is not local to itself to some Master MTA within
the PRMD which figures out the correct routing from there. Or some other scheme.
The CCITT X.400 spec is silent on how the mail gets there as long as it gets
there.

Bob Leone
Soft Switch