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PTR Record

Posted on 2010-03-25
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Last Modified: 2013-12-05
We currently send mail directly through DNS lookup on our exchange box.

We get blocked by like AOL and hotmail for not having a PTR record from what I can see.

if I check the PTR for our public IP it comes up as
hostXXX-XXX-XXX-XXX.in-addr.btopenworld.com

With the XXX being the IP.

Does this need to be the domain that we are sending email from?

I've tried contacting BT support but they didnt even know what a PTR record is.

Our actual domain we send from is hosted elsewhere as we use them for POP mail.

Thanks in advance.
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Question by:andrewmilner
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by:Glen Knight
ID: 28559358
It should really match the A record that your MX record uses.

for example your MX record should point to an A record like mail.domainname.com

You then need to ask your ISP (BT Openworld) to setup an rDNS(PTR) record for your IP address of mail.domainname.com

I have an article here that should help: http://www.experts-exchange.com/articles/Software/Server_Software/Email_Servers/Exchange/Exchange-DNS-Configuration.html
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Expert Comment

by:Glen Knight
ID: 28559471
>>I've tried contacting BT support but they didnt even know what a PTR record is.
This is not unusual.  I have lots of problems with BT
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Expert Comment

by:yousef_ad
ID: 28559513
if u have windows dns check..
when you add A host record. you must check the box for add PTR Record..

-From DNS Manager, open your forward zone.
-Right-click on the "A" record for your DNS server, and then click Delete Record.
-Click Yes to confirm the deletion of the "A" record.
-Right-click on the forward zone, and then click New Host.
-Type the host name of your DNS server and the IP address.
-Select the Create Associated PTR Record check box.
-Click Add Host, and then click Done.


if unix check

this is for the zone..write inside named.conf

zone “1.168.192.in-addr.arpa” {
   type master;
   notify no;
   allow-query { any; };
   file “192-168-1.zone”;
};
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Expert Comment

by:Glen Knight
ID: 28559713
The comment above is not relevant for sending e-mails out of your organisation.
This is talking about INTERNAL DNS not EXTERNAL DNS
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Author Comment

by:andrewmilner
ID: 28560286
Sweet.  Thanks for the comments guys.

So I need to change the A record of the domain to point back to the IP of where the mail is originating? ie our public mail server IP that we have in our building?

Is it simpler to change our mail server announce to what the PTR currently is for the IP?


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Expert Comment

by:Glen Knight
ID: 28560593
No, all you need to do add a Reverse DNS record for the same name as your A record that the MX record uses.
Please follow my guide.
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Author Comment

by:andrewmilner
ID: 28563474
are you saying to put mail.mydomain.com as the ""A"" record  or nameserver racord?  so we dont put the IP in the A record then?
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by:Glen Knight
ID: 28563648
OK, you haven't read my article yet?

this is how it should look:

A Record = mail.domainname.com IP of 111.222.111.222
MX = mail.domainname.com
rDNS = mail.domainname.com
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Author Comment

by:andrewmilner
ID: 28564429
I did read - just want to be sure :-P

we use an external POP 3 mailserver different to the one we use to send

Please ammend above

Also if I go to change the A record then it only allows me to put an IP in not a name
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Expert Comment

by:Glen Knight
ID: 28564621
The A record WILL only allow you to specify an IP address.
You don't need to change this.
You need to add an rDNS record that is the same name as your A record that the MX record uses.
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Author Comment

by:andrewmilner
ID: 28568405
The MX needs to remain pointing at the external server IP otherwise we wont get mail.
I have asked BT to add the PTR for our public facing IP to be mail.ourdomain.com

You need to add an rDNS record that is the same name as your A record that the MX record uses.
How does an MX record use an A record?
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Expert Comment

by:Glen Knight
ID: 28568536
An MX record MUST use an A record.  This is all explained in my article.
An MX record should not be pointing to an IP address the A record should point to the IP address and the MX record to the A record.
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Author Comment

by:andrewmilner
ID: 28569604
So..

A Record is set to our public IP
MX has to stay as IP of 3rd party hosted pop server
PTR of OUR Ip is set to mail.domain.com

Am I missing anything?
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Expert Comment

by:Glen Knight
ID: 28569797
Your MX record should point to an A record.
If you have to configure that A record to the IP of your 3rd party hosted service then that's fine.
Your PTR record should then be the same as the A record.

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Author Comment

by:andrewmilner
ID: 28570623
I thought the MX record is whas is used by people wanting to send us mail, so if we change the MX record to something other the actual mail server that we get email from then how is incoming mail going to work?
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Glen Knight earned 2000 total points
ID: 28571058
Right, according to RFC2181 This domain name must have as its value one or more address records. Currently those will be A records, however in the future other record types giving addressing information may be acceptable.  It can also have other RRs, but never a CNAME RR."

if you read the rest of section 10.3 http://tools.ietf.org/html/rfc2181#section-10.3 it also goes on to say that your MX record should not be configured to use an IP address.

This is where the A record comes in.
You configure the A record (it makes absolutely no difference what this A record is called as long as it is something.domainname.com) to use the IP address of your 3rd party hosting service.
Then you configure the MX record to use this A record.  This means that your mail will still go to the same place it's going now.

You then ask your ISP to configure a rDNS record for your IP address that's the same as the A record you created above for your MX record.

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