>This comment was added as a follow-on note. Sorry for not being clear.
>
>Accepting messages from a domain lacking MX records might be risky
>due to the high rate of domain turnovers. Within a few weeks, more
>than the number of existing domains will have been added and deleted
>by then. Spammers take advantage of this flux. Unfortunately SMTP
>server discovery via A records is permitted and should be
>deprecated.
All it would require is a couple of large ISP's to adopt
such a policy. "MX 0 <self>" really is not hard and benefits
the remote caches.
>Once MX records are adopted as an _acceptance_
>requisite, domains not intended to receive or send email would be
>clearly denoted by the absence of MX records. SMTP policy published
>adjacent to MX records also eliminates a need for email policy
>"discovery" as well. Another looming problem.
Better yet us MX records to signal that you don't want to
receive email e.g. "MX 0 .". It has a additional benefits
in that it is *much* smaller to cache than a negative
response. It's also smaller to cache than a A record.
Since all valid email domains are required to have a working
postmaster you can safely drop any email from such domains.
>Don't accept a message from a domain without MX records. When there
>is no policy record adjacent to the MX record, there is no policy,
>and don't go looking.
>
>-Doug
>
