Hi everyone.

We have been accepting mail for several domains now, and mail has been coming in successfully from a million different sources to those domains (as it should!). But now that our pop server is behind a load balancer, it's saying "relay not permitted". We've fixed this issue in DNS for the customers whose DNS we control, but it's still a baffling problem.

We have a a pretty standard configuration (the part quoted below is from the default configuration, I recall), and the server should accept mail from anywhere that isn't on a DNSBL. It also results in a completely different error message when it's rejected by a DNSBL, so I don't understand where this one is coming from.

So here's my configuration. First we have the ACL that actually does the rejecting:

  require
    message = relay not permitted
    domains = +local_domains : +relay_to_domains

Then the router that does the DNS lookup to determine if we're the real recipient for that domain:

dnslookup_relay_to_domains:
  debug_print = "R: dnslookup_relay_to_domains for $local_part@$domain"
  driver = dnslookup
  domains = ! +local_domains : +relay_to_domains
  transport = remote_smtp
  same_domain_copy_routing = yes
  no_more

# deliver mail directly to the recipient. This router is only reached
# for domains that we do not relay for. Since we most probably can't
# have broken MX records pointing to site local or link local IP
# addresses fixed, we ignore target hosts pointing to these addresses.

dnslookup:
  debug_print = "R: dnslookup for $local_part@$domain"
  driver = dnslookup
  domains = ! +local_domains
  transport = remote_smtp
  same_domain_copy_routing = yes
  # ignore private rfc1918 and APIPA addresses
  ignore_target_hosts = 0.0.0.0 : 127.0.0.0/8 : 192.168.0.0/16 :\
                        172.16.0.0/12 : 10.0.0.0/8 : 169.254.0.0/16 :\
                        255.255.255.255
  no_more

.endif


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