Reverse MX proposition has been updated after this.
4.3.2.1.in-addr.arpa IN PTR mail.company.dom.
4.3.2.1.in-addr.arpa IN MX 10 127.0.0.2
127.0.0.2=Allow, 127.0.0.3=Deny
BTW (and I was guilty of this the other day too.. but didn't occur
to me until a little after posting): the target of an MX is a name,
not a number. "127.0.0.2" can be used, but it doesn't mean an IP
address. Perhaps some use could be made of the reverse MX pointer
indicating some legitimate name.
mm
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