Douglas Otis wrote:
This avoids the myriad of SMTP opt-out strategies such as
"MX .", "TXT v=spf1 -all", or "TXT DKIM=DISCARDABLE".
Digression, finally I recall a technical problem (above the
clear disadvantages of opt-out at least for IPv6) with the
null-MX idea, one of those weird "alternate roots" managed
to have an IPv4 (A record) for its wannabe-root.
Frank
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