If an incorrect domain name is in an author or return handling
address, there are bigger problems to solve than AAAA/MX.
Indeed, this is the problem - the problem is that such
misconfiguration doesn't get detected since the address *seems* to
work just fine.
The mail is "received", but disappears into some never-seen /var
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 construct.
If someone is sending out invalid email addresses, then that needs
to get fixed, rather than working on some post-hoc mechanism.
The problem is that fixing this is made much more difficult than
necessary by having the AAAA record.
Thus, disabling AAAA checking seems to provide much cleaner error
Let's do it for all Internet services, not just email.
Yes, some other time. Email just seems particularly prone to this
problem due to the SMTP retry behavior. Most other services don't try
for a week.
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