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  • Email rejected

    Hi,
    We are receiving this bounce back from this one particular external domain.

    smtp;550 No RDNS entry for 175.a.x.141

    our mx : mail.x.shm.com = 175.a.x.140

    our ptr : 175.a.x.140 = mail.x.shm.com

    175.a.x.141 is our WAN 1 interface of the firewall.

    Why does the external domain reject the RDNS.

  • #2
    Your MX record designates where email goes TO for your domain, not where it comes FROM for your domain. It looks to me like your firewall is NAT'ing your email servers outbound traffic to 175.a.x.141, not to 175.a.x.140 as you are assuming it is. You should check the NAT rule that is being applied to your email server for outbound traffic.

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    • #3
      Yes, that is correct.
      We have 5 public IP.
      .140 map to Exch Server
      .141 is WAN1 interface

      All internal internet access is going out using .141
      You're suggesting that all Internal -> WAN1 is using .140?
      Or only Exch Server going out using .140

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      • #4
        I'm suggesting that while you may have .140 mapping to your Exchange server for INBOUND traffic you should verify that it is mapping .140 to your Exchange server for OUTBOUND traffic. On the Exchange server go to the website www.ipchicken.com and see what ip address it shows. That is the ip address that is being mapped to your Exchange server for OUTBOUND traffic.

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        • #5
          Done. Exch Server now Inbound and Outbound using .140.
          The rest is .141
          The email also go through to the external domain.
          Thanks.
          Closed

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