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Conditional SMTP

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  • Dominique
    Hi, Due to problems with my ISP, I am trying to split my outgoing mail between two relays. The bulk of my mails goes out through relayhost (Dyn SMTP service),
    Message 1 of 2 , Feb 25, 2013
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      Hi,

      Due to problems with my ISP, I am trying to split my outgoing mail
      between two relays.
      The bulk of my mails goes out through relayhost (Dyn SMTP service),
      while a small problematic domains (Dyn server being blacklisted) goes
      out through another server (with the ISP mail server).From what I
      understood from the manual, outgoing priorities will check
      transport_maps first then will fallback to relayhost.

      In my main.cf file, I have the following 2 entries:
      relayhost = outbound.mailhop.org
      transport_maps = hash:/etc/postfix/transport

      The latter one with my ISP smtp server info for for my conflictive
      domainin the following format:

      domain.com smtp:smtp.isp.com

      With the valid entries in
      smtp_sasl_password_maps = hash:/etc/postfix/sasl_passwd
      for authorization

      Although it seems to be working (i.e. I can send mail from both -
      checked from mail.log - both mails are being received), the outgoing
      mail through transport_maps also keeps being recycled until I finally
      receive an error message:

      Undelivered Mail Returned to Sender
      host smtp.isp.com said: 552 5.7.0
      Number of 'Received:' DATA headers exceeds maximum permitted (in reply to
      end of DATA command)

      Where am I going wrong ?

      Thanks for the insight,

      Dominique
    • Viktor Dukhovni
      ... Since ISP SMTP relays are generally provisioned for MSAs that don t do MX lookups, you should probably use: domain.com smtp:[smtp.isp.com] likely over
      Message 2 of 2 , Feb 25, 2013
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        On Mon, Feb 25, 2013 at 11:59:40AM +0100, Dominique wrote:

        > The latter one with my ISP smtp server info for for my conflictive
        > domainin the following format:
        >
        > domain.com smtp:smtp.isp.com

        Since ISP SMTP relays are generally provisioned for MSAs that don't
        do MX lookups, you should probably use:

        domain.com smtp:[smtp.isp.com]

        likely over port 587 with TLS.

        > With the valid entries in
        > smtp_sasl_password_maps = hash:/etc/postfix/sasl_passwd
        > for authorization
        >
        > Although it seems to be working (i.e. I can send mail from both -
        > checked from mail.log - both mails are being received), the outgoing
        > mail through transport_maps also keeps being recycled until I
        > finally receive an error message:
        >
        > Undelivered Mail Returned to Sender
        > host smtp.isp.com said: 552 5.7.0
        > Number of 'Received:' DATA headers exceeds maximum permitted (in reply to
        > end of DATA command)

        One of the recipients forwards the mail back to your server, which forwards
        to the recipient, ... Find the loop. Look for the outgoing message-id
        (not queue-id) in later incoming messages.

        --
        Viktor.
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