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I am getting a lot of mail bounced back mails. The bounced message says:

We cannot accept email from IP 213.42.234.186 without a DNS PTR record. Contact your ISP/HSP to set up a PTR record for your server.

I have verified that our mail server (mail.royalgroup.ae) is listed as the PTR record for the IP in question. What I don't understand is why the IP address of our firewall (.186) is listed in the bounce message.

I have included the whole bounced message with headers below.

-------------------------------------------------------------------------- MDaemon Delivery Status Notification - http://www.altn.com/dsn/
--------------------------------------------------------------------------

The attached message had PERMANENT fatal delivery errors.

After one or more unsuccessful delivery attempts the attached message has been removed from the MDaemon mail queue on this server.  The number and frequency of delivery attempts are determined by local configuration.

-------------------------------------------------------------------------- YOUR MESSAGE WAS NOT DELIVERED TO ONE OR MORE RECIPIENTS
--------------------------------------------------------------------------

Failed address: [email protected]

--- Session Transcript ---  Tue 2013-04-23 08:27:00: Parsing message <xxxxxxxxxxxxxxxxxxxxxxxx\pd35000094660.msg>  Tue 2013-04-23 08:27:00:
*  From: [email protected]  Tue 2013-04-23 08:27:00: *  To: [email protected]  Tue 2013-04-23 08:27:00: *  Subject: a  Tue 2013-04-23 08:27:00: *  Size (bytes): 32512  Tue 2013-04-23 08:27:00:
*  Message-ID: <002d01ce3fdb$53e0eb40$fba2c1c0$@ae>  Tue 2013-04-23 08:27:00: Attempting SMTP connection to [mail.ru]  Tue 2013-04-23 08:27:00: Resolving MX records for [mail.ru] (DNS Server:
213.42.20.20)...  Tue 2013-04-23 08:27:00: *  P=010 S=000 D=mail.ru TTL=(8) MX=[mxs.mail.ru] {94.100.176.20}  Tue 2013-04-23 08:27:00: Attempting SMTP connection to [94.100.176.20:25]  Tue 2013-04-23 08:27:00: Waiting for socket connection...  Tue 2013-04-23 08:27:00: * Connection established (127.0.0.1:3187 -> 94.100.176.20:25)  Tue 2013-04-23 08:27:00: Waiting for protocol to start...  Tue 2013-04-23 08:27:01: <-- 220 Mail.Ru ESMTP  Tue 2013-04-23 08:27:01: --> EHLO mail.royalgroup.ae  Tue 2013-04-23 08:27:01: <-- 250-mx142.mail.ru ready to serve  Tue 2013-04-23 08:27:01: <-- 250-SIZE 73400320  Tue 2013-04-23 08:27:01: <-- 250 8BITMIME  Tue 2013-04-23 08:27:01: --> MAIL From:<[email protected]> SIZE=32512  Tue 2013-04-23 08:27:02: <-- 250 OK  Tue 2013-04-23 08:27:02: --> RCPT To:<[email protected]>  Tue 2013-04-23 08:27:02: <-- 250 OK  Tue 2013-04-23 08:27:02: --> DATA  Tue 2013-04-23 08:27:03: <-- 354 Go ahead  Tue 2013-04-23 08:27:03: Sending <xxxxxxxxxxxxxxxxxxxxxxxx\pd35000094660.msg> to [94.100.176.20]  Tue 2013-04-23 08:27:03: Transfer Complete  Tue 2013-04-23 08:27:05: <-- 550 We cannot accept email from IP 213.42.234.186 without a DNS PTR record. Contact your ISP/HSP to set up a PTR record for your server.  Tue 2013-04-23 08:27:05: --> QUIT
--- End Transcript ---
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3 Answers 3

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Your firewall is most likely a transparent SMTP proxy for filtering spam and viruses. Add a PTR record for the firewall's external IP. While you're at it, make sure you're updating your SPF record (if any).

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  • Sorry Sir I didn't get you, how can i solve it where i have to go for add PTR record ,my firewall model is Sonic-wall 2400 and my mail server is Mdaemon version 11.0. I am getting this bounced message only from some domain Example i cannot send any mail to *[email protected]
    – user170765
    Apr 23, 2013 at 8:49
  • A PTR record is, in DNS speak, a reverse record that enable the lookup of a host name based on an IP address. Some mail admin goes by the belief that requiring a PTR record for connecting email server lower the amount of spam. It has therefore become a common step to prepare such a record for any server that will send out message in behalf of your domain. Unfortunately, you can't set it up yourself: it has to be done by your ISP.
    – Stephane
    Apr 23, 2013 at 9:02
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You need to ask your datacentre or ISP to add PTR record for your mail server IP wghich is 213.42.234.186

So when someone do nslookup 213.42.234.186 it should get resolved to your mail server hostname.

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I have verified that our mail server (mail.royalgroup.ae) is listed as the PTR record for the IP in question

Not from here it isn't...

** server can't find 186.234.42.213.in-addr.arpa.: NXDOMAIN

And you don't have SPF configured.

What I don't understand is why the IP address of our firewall (.186) is listed in the bounce message.

Have you checked to see what IP address is on the packets on the other side of the router? Most likely it's been configured to masquerade.

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