Our MX currently relays to one of two boxes (mail1, mail2) based on a list of domains in transport_maps. Both mail1 and mail2 are ours, and we have a full list of domains and recipients in relay_domains and relay_recipient maps respectively.

Now, I would like to add a third, external, relay destination for one domain. I can add the domain to relay_domains, but would prefer to use address verification for the recipients (in that domain only).

My current restrictions:

smtpd_recipient_restrictions =
 reject_unauth_destination,
 reject_unlisted_recipient,
 check_recipient_access hash:/etc/postfix/maps/rfc_addresses,
 reject_non_fqdn_helo_hostname,
 reject_invalid_helo_hostname,
 reject_non_fqdn_sender,
 check_client_access pcre:/etc/postfix/maps/reverse_dns.pcre,
 reject_unknown_sender_domain,
 check_client_access pcre:/etc/postfix/maps/generic_rbl_clients.pcre,
 check_sender_access hash:/etc/postfix/maps/backscatter_senders,
 reject_rhsbl_client dbl.spamhaus.org,
 reject_rhsbl_helo   dbl.spamhaus.org,
 reject_rhsbl_sender dbl.spamhaus.org,
 check_policy_service unix:private/policyd-spf,
 check_policy_service unix:private/postgrey,
 permit

My first question is, what effect does reject_unverified_recipient actually have? For example, if the recipient is verified, do the restrictions continue to be evaluated, or is it the equivalent of an OK? If the other restrictions are evaluated, wouldn't the address still be rejected by either reject_unlisted_recipient or the default smtpd_reject_unlisted_recipient=yes?

Regardless of the answer to that question, where is the smartest place to stick that restriction in my current list? I would prefer to add something like,

  check_recipient_access hash:/.../recipient_verify_domains

containing,

  example.com   reject_unverified_recipient

so that only that domain's addresses are verified. However, this depends on whether or not the reject_unlisted_recipient is skipped. If it isn't, should I move the reject_unlisted/unverified restrictions to the end? Or create a separate (almost-identical) restrictions class for the domain in question?

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