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Reverse DNS change with my ISP (PTR Record)

Posted on 2009-07-13
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Last Modified: 2013-12-09
Hello!
I run a site and a webserver on a same PC and on the same IP.I got an e-mail from some whitelisting site suggesting that I should ask my ISP (who gave me the static IP) to make sure that reverse DNS lookup will be resolving to my mail server host name and NOT my ISP's default generic host name.The domain name registrar Co. is NOT my ISP.
So I have 2 questions:
1) Should I bother with all of this? Is there a chance that something will go wrong since I have BOTH web AND e-mail servers sitting on the same IP...
2)If I should...and if it won't hurt anything...should I make reverse DNS pointing to my domain name or mail server's host name,which is mail.mydomainname.com?
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Question by:abrodski
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3 Comments
 
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Expert Comment

by:giltjr
ID: 24845416
It does not matter who your domain name registrar is, they have nothing to do with the reverse lookups (PTR records).  The owner of the IP address should be running the DNS server that controls the PTR records for their IP addresses.

It is a good idea to have the IP address of your outbound SMTP server have a PTR record that resolves to either its host name or your domain name.

Some e-mail servers will only accept e-mail if the reverse look-up for the sending IP address maps to the domain name that is in the MAIL FROM command.  Some e-mail servers will do a reverse look-up and then do a forward look-up on the results and make sure they point to each other.
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Author Comment

by:abrodski
ID: 24845469
"It is a good idea to have the IP address of your outbound SMTP server have a PTR record that resolves to either its host name or your domain name"

That's what I don't understand here...If I have BOTH web and e-mail servers on the same IP and on the same physical machine (PC)...so this reverse DNS thing should point to what? domain name or my e-mail server's host name (ie mail.mydomain.com)?
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giltjr earned 500 total points
ID: 24845507
It should point to your e-mail server's name (mail.mydomain.com) or just your domain name (mydomain.com).  Nobody really does reverse look-ups for IP address other than for e-mail.
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