SM wrote:
This reply is off-topic and is not related to the current rfc2821-bis
discussion.
Yes. We should start another list.
host -t txt f098474401a124aa5a2738b6353e22da.example.com._vrfy.example.com
where f098474401a124aa5a2738b6353e22da is a MD5 hash of the email
address. That's to avoid disclosing the actual email address.
I like it.
Queries for the zone can be restricted to the DNS server used by the
secondary MX.
Actually, this would be generally useful, not just for a secondary MX.
The lookup could return more than one piece of information. For
example, it could say:
o This address will be accepted in a RCPT command.
o This address should be accepted in a MAIL command.
For example, we have an e-mail address "sales(_at_)roaringpenguin(_dot_)com"
that's only used for inbound mail; we never send mail from that
address. Being able to specify via DNS that MAIL
FROM:<sales(_at_)roaringpenguin(_dot_)com> is a forgery would be useful.
In addition, allowing SMTP servers to more quickly reject recipient
addresses is useful; if an ISP can quickly reject a recipient based on
a DNS lookup rather than attempting an SMTP session, it can save
resources.
It may not scale well for a site with a lot of email addresses.
Why not? People operate RBLs with many thousands of entries and the
DNS handles it fine. A site with a lot of e-mail addresses *must* do
a directory lookup at some point, so it must have the infrastructure
to do it efficiently.
Regards,
David.