I have a question about smtp_defer_if_no_mx_address_found. Our cloud-based app servers handle application-specific mail that's destined for them, and these servers aren't static -- new ones are brought up and old ones are shut down as needed. A special internal MX record (I'll call it app-mx.host.com) tracks which servers are currently available to receive mail. app-mx.host.com does not have an associated A record because there is no single machine that represents that domain name.
Now there should never be a case where all servers are dropped from the MX record, but if it does occur, we'd like our Postfix instances to defer the message and retry. I thought smtp_defer_if_no_mx_address_found would handle it, but testing that out, the message bounces because of the lack of an A record (or any record for that matter). In that case, I get the following log message: Jul 31 13:28:07 ip-xx-yy-zz-aa postfix/smtp[1608]: 3E9281CA4: to=< a...@host.com>, relay=none, delay=0.01, delays=0.01/0/0/0, dsn=5.4.4, status=bounced (Host or domain name not found. Name service error for name= app-mx.host.com type=A: Host not found) Is there a configuration that will do what I want -- if a domain doesn't exist at all, Postfix will defer rather than bounce? Thanks, Drew
