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Email Server Reverse IP DNS Setup

Posted on 2014-09-09
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Last Modified: 2014-09-09
Hello,

I have a question regarding the need for setting up reverse DNS on a static IP for outgoing email.  We have an Exchange email server setup that will be utilizing a DSL connection.  We have a static Public IP setup so that we can send and receive email. However the DSL provider does not allow us to setup a reverse DNS entry so that the static IP maps to the A record of our email server.  It is best practice to have this in place but I'm wondering how likely we are to experience problems sending people outside of our organization email if the reverse DNS entry isn't setup? What are your thoughts?

Thank you.
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Question by:jledbetter
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by:Seth Simmons
Seth Simmons earned 125 total points
ID: 40312963
i haven't seen too many do a PTR record check
most of the checks are usually for SPF records to verify the sending server
that you can do on your own; you don't need your ISP to create that - unless your ISP manages your external DNS

Sender Policy Framework
http://www.openspf.org/SPF_Record_Syntax
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by:Neil Russell
Neil Russell earned 125 total points
ID: 40312971
LOTS do reverse lookups! at one point we got about 10% of all outbound bounce because others used 3rd party anti spam solutions that did this and rejected on failure.

For instance AOL.


"554 RTR:RD
The reverse DNS of your IP Address is typical of a dynamic IP Address and/or has generated AOL Member complaints. Ensure you have a fully qualified domain name and get approved for a complaint feedback loop before opening a support request.
rDNS must be in the form of a fully-qualified domain name. rDNS containing in-addr.arpa are not acceptable, as these are merely placeholders for a valid PTR record. rDNS consisting of IP addresses are also not acceptable, as they do not correctly establish the relationship between domain and IP address.
rDNS that may be similar to dynamic IP space (containing pool, dhcp, dyn, etc.) may be treated as suspect, and should therefore should be changed to reflect a fully-qualified domain name with standard reverse DNS."

421 DNS:NR
The Reverse DNS lookup for your IP address is failing. This could be a transient issue. Confirm the IP that sends your mail. Then check the rDNS of that IP using our troubleshooting tools. If it passes, please wait 24 hours and re-try before opening a support request.
rDNS must be in the form of a fully-qualified domain name. rDNS containing in-addr.arpa are not acceptable, as these are merely placeholders for a valid PTR record. rDNS consisting of IP addresses are also not acceptable, as they do not correctly establish the relationship between domain and IP address.
rDNS that may be similar to dynamic IP space (containing pool, dhcp, dyn, etc.) may be treated as suspect, and should therefore should be changed to reflect a fully-qualified domain name with standard reverse DNS.


http://postmaster.aol.com/Postmaster.Errors.php
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by:footech
footech earned 125 total points
ID: 40312992
I've heard of a lot more mail failing to be delivered due to incorrect or missing PTR records than I have due to SPF issues.  Not having a SPF is not likely to hurt you, whereas having an incorrectly configured SPF certainly could.
As far as PTR records, some receivers only check that a PTR record is present, whereas others check that the PTR record matches an A record (forward confirmed reverse DNS), and some don't care at all.  Unfortunately I don't have any statistics as to what percentages of receivers may block your mail because of different issues.  If I had to guess I might say around 5% would block without a PTR record, but I could be way off.
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Alan Hardisty earned 125 total points
ID: 40313020
It is an RFC requirement to have Reverse DNS setup when you have an email server - if your ISP won't provide it, you need to change ISP's to one that does, or you will have to use a SMARTHOST to send all your emails to for them to forward on to the final recipients, which is a pain, but should avoid email rejection.

Alan
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by:jledbetter
ID: 40313025
Thank you for everyone's timely feedback. It sounds like we will need to research other internet providers that can provide the ability to manage reverse DNS lookups.
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