From RFC 2821:
Any system that includes an SMTP server supporting mail relaying or delivery MUST support the reserved mailbox “postmaster” as a case-insensitive local name.
The rfc-ignorant blacklist may list domains that do not have certain required role addresses.
Technically speaking, postmaster mail for DH-hosted domains should go to the DH postmaster, as they’re the ones responsible for the mail systems. Some hosts automatically set up certain addresses to go to them rather than the customer (eg, postmaster, abuse, root). DH does not.
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