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Problem with rDNS settings

I manage all DNS settings on my network.  Currently, my users are experiencing issues when e-mailing Comcast users.  The error returned is a 554 error.   "554 IMTA21.emeryville.ca.mail.comcast.net comcast       Comcast requires that all mail servers must have a PTR record"  I thought I had all rDNS settings set up the way they needed to be.  Can someone tell me what my A record should look like for a mail domain?

My current record looks like:
mail.servername.org     A     IN

1 Solution
wimilesAuthor Commented:
It appears as though this is a tough question, or I did not explain the issue out enough or correctly.  Please advise how to re-word this to make it more understandable.
AOL, EarthLink, Comcast -and few others always have had a hue and cry about setting a PTR else they would not accept the messages.

So, create a reverse lookup zone and have a PTR Record setup to resolve your A record (Host Name) to it. Also, have it published by talking to your ISP to host this on their records, so over the internet this information should be available.

you don't have reverse record defined. unless you "own" your IP block, it is your ISP you need to ask to create reverse PTR record for you. if you search the web for PTR records you will find plenty of information available
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you'll have to create a zone for your IP block, in the example below i'm using a single IP reverse zone for the IP 123.456.789.22


the above mentioned zone should have PTR typed records, as in the example below;

@ PTR mydomain.com

PTR records are used by a mailserver to look if the connected client is spoofed or not, the mailserver checks the connected IP and the domain in the FROM header and confirms it from RDNS(PTR) entries if the domain in the FROM header is actually bound to the IP connected.

you can find more information about RDNS entries from


excellent article explaining RDNS setup
wimilesAuthor Commented:
This was exactly what I needed.  Thank you.
thnaks mate

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