Hi John,
At 07:44 18-07-2014, John Levine wrote:
Well, OK. What would be the proper MX for mail sent to
ted(_at_)www(_dot_)ietf(_dot_)org ?
That's a good question. I'll explain the problem as follows:
(a) The user uses an incorrect email address for the recipient.
(b) The mail service does not provide timely feedback about not
being able to deliver the message (see (a)).
The fix proposed is to signal that the mail target does not support a
mail service. It's not a bad idea. Now, how do you (used in a
general sense) do that? Currently, there isn't any way to do that
because of the implicit MX. There was a fix proposed over nine years
ago. It was to use a dot as the mail target. From an application
point of view, what the dot means is a DNS problem. :-) From a SMTP
point of view, the target host is not valid; the user will be sent a
message in about four hours with information about the delivery status.
The MX RDATA format, defined in an Internet Standard, is as follows:
"A <domain-name> which specifies a host willing to act as a
mail exchange for the owner name."
There is a problem. The IETF can:
(a) Solve it.
(b) Pretend that it does not exist.
(c) Wait.
I do not have a strong opinion about all.
Regards,
S. Moonesamy