Question : 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 204.38.104.10       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     1.1.1.1

Answer : Problem with rDNS settings

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

22.789.456.123.in-addr.arpa

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

http://www.crucialp.com/resources/tutorials/web-hosting/how-reverse-dns-works-rdns.php

excellent article explaining RDNS setup