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Re: smtp_defer_if_no_mx_address_found'

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  • Wietse Venema
    ... It s called soft_bounce=yes. Use with care: this will defer ALL bounces including user unknown and other errors. smtp_defer_if_no_mx_address_found is for
    Message 1 of 3 , Jul 31, 2013
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      Drew Mazurek:
      > Is there a configuration that will do what I want -- if a domain doesn't
      > exist at all, Postfix will defer rather than bounce?

      It's called soft_bounce=yes. Use with care: this will defer ALL
      bounces including "user unknown" and other errors.

      smtp_defer_if_no_mx_address_found is for the case that the MX record
      DOES exist, but the MX hostname has no IP address. In your case the
      MX record does not exist.


      Wietse
    • King Cao
      This is the behavior of Postfix: the mail will be returned to sender if the destination can t be found but will be deferred if the destination can t be
      Message 2 of 3 , Jul 31, 2013
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        This is the behavior of Postfix: the mail will be returned to sender if the destination can't be found but will be deferred if the destination can't be reachable. 

        It's different between NOT FOUND and CAN'T BE REACHABLE. NOT FOUND means send NDR to sender (situation you meet now), but CAN'T BE REACHABLE means defer and retry. So please change your transport file to:
         a) Use one internal A record (eg: app.host.com), and such A record point to all your app servers:
                     *          smtp:[app.host.com]:25
        Or b) try below format (below format will query MX record):
                     *          smtp:app-mx.host.com:25

          


        2013/8/1 Drew Mazurek <drew@...>
        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=<addr@...>, 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

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