John Leslie wrote:
The information that is transferred during the retained SMTP exchange
is minimally helpful, except for previous-hop IP Address.
Please don't forget the URI and RFC2821MailFrom. These tell you the
MailFrom does not always specify originator. Let's not repeat the SPF
Everything else requires access to the actual message. This means
reaching across the net to get the message for inspection.
Yes, there is a TCP setup time involved here. How responsive that
server is is presumably under the control of the originator.
and extra cost on the receive side.
The issue of hand-off responsibility is changed, but I have not heard
that asserted as a problem amidst anti-abuse efforts.
You must be following different mailing lists than I do. I have seen
rather a bit of traffic about how to hold a SMTP connection open for
a longer time.
Citations to this constituency, please?