Henning Schulzrinne wrote:
One of the problems I have seen first-hand is "disappearing" mail.
Example: A webserver sends outbound email directly, but doesn't want
to receive inbound email. The hostname leaks and mail gets sent to
that address, based on the A(AAA) record.
What do you mean by "leaks"?
If it means something other than the domain name of the webserver appears in
author's rfc2822.From field address (or, of course, the rfc2822.Reply-To field)
then your scenario doesn't happen, because those are the only fields that get
used for return email from a recipient.
Same if/then, with respect to rfc2821.mailfrom and handling notices.
If an incorrect domain name is in an author or return handling address, there
are bigger problems to solve than AAAA/MX.
If you mean yet something else, then what?
The mail is "received", but
disappears into some never-seen /var file.
So, a domain name erroneously appears in an address field and the references
host erroneously accepts mail it shouldn't.
This degree of problematic operation is not likely to get solved with a new DNS
If someone is sending out invalid email addresses, then that needs to get
rather than working on some post-hoc mechanism.
Thus, disabling AAAA checking seems to provide much cleaner error
Let's do it for all Internet services, not just email.
IETF mailing list