[db-wg] Changes for abuse

Randy Bush wrote:

> > no TLD's that accept e-mail.
> 
> please do not add restrictions which are not in the protocol.

agreed in the spirit of RFC 3696, if nothing else.

> and there are current email recipients of the form user at tld.

As an exercise that's fine, but in this particular case it is calling
for trouble. There are some role addresses that should have lower access
thresholds, so I'm fine with the test. Even more, it might be useful
to check whether the address given ends in a valid TLD and/or an MX RRSet for
the domain name eists.

-Peter

PS: VA had postmaster at va in their SOA and years ago and at that time there
    was quite some debate about pros and cons already.