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Re: backup/fallback for default_transport ?

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  • Noel Jones
    ... relayhost specifies a destination, default_transport specifies a delivery channel. Seems to me you should be using relayhost, but it probably doesn t
    Message 1 of 7 , Jun 26, 2012
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      On 6/26/2012 3:46 PM, lutz.niederer@... wrote:

      >
      > Except for the [transport] with default_transport where do relayhost and default_transport differ in that scenario? Especially if I can also set relay_transport...

      relayhost specifies a destination, default_transport specifies a
      delivery channel. Seems to me you should be using relayhost, but it
      probably doesn't matter much.

      >
      > Does it cycle through the 2 A/MX records (IPs) when trying to deliver? Does it try both on each try or does it try one, wait, two, wait, one, ...

      http://www.postfix.org/OVERVIEW.html#delivering

      During each delivery attempt, postfix will try MXs in order of
      precedence[1]. In the case of one primary and one secondary,
      postfix will always try the primary first. If the primary is
      unavailable or the connection times out, postfix will immediately
      try the secondary.

      If you define two equal-weight MXs (or two A records with no MX),
      postfix will randomly pick one. If postfix's first choice is
      unavailable, postfix will then try the second.

      [1] there are sanity limits on how many MXs postfix will try.
      http://www.postfix.org/postconf.5.html#smtp_mx_address_limit
      http://www.postfix.org/postconf.5.html#smtp_mx_session_limit



      -- Noel Jones
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