At 17:56 -0400 on 09/07/2005, John C Klensin wrote about Classifying
gateways in 2821/ 2821bis:
(iii) A gateway, defined as a transition/ translation
point between an SMTP environment and a non-SMTP
environment, as noted above. The expectation is that
gateways will only make those changes to message bodies
(including headers) that are actually necessary to
preserve the maximum amount of information as the
message passes from one environment to another.
Gratuitous "improvements" are inappropriate for
gateways, too.
I guess the AoL Email Gateway falls this "preserve the maximum amount
of information" requirement since it does not covert a DNT Header
into a RRR Flagged Message for incoming messages from the Internet,
Create a DNT Header in RRR Flagged Messages it injects into the
Internet SMTP Server, and when presented with a incoming message from
the Internet that has more than one attachment, it does not covert
all the attachments into one Archived File unlike what occurs with
multi-attachment messages created on the AoL side of the Gateway,