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Reverse DNS Failed ! This is a Problem. (report from www.mxtoolbox.com) plz Help

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Reverse DNS Failed ! This is a Problem. (report from ww... - 7.Feb.2009 7:46:26 AM   
itguyme

 

Posts: 25
Joined: 1.Apr.2006
Status: offline
Hi Guys,
I went to www.mxtoolbox.com and put my mail server (http://mail.psu.edu.sa) there only to find the messenge :

Reverse DNS Failed ! This is a Problem

I am having problems with my outbound emails as they leave our network never to reach their recipients in some cases. Please help.

What is the significance of this error
Post #: 1
RE: Reverse DNS Failed ! This is a Problem. (report fro... - 7.Feb.2009 1:49:35 PM   
uemurad

 

Posts: 8232
Joined: 7.Jan.2004
From: California, USA
Status: offline
Some recipient systems use Reverse DNS lookups to verify the sender.  This helps reduce the amount of spam being allowed in.

How it works is, when a sending system makes a connection to the recipient system, the recipient system notes the sending IP address and performs a reverse lookup.  In other words, queries the public DNS for the Fully Qualified Domain Name (FQDN) connected to that IP address.  If the sending SMTP address matches the FQDN, then it's much more likely that the message is legitimate and therefore is allowed in.  If the SMTP address doesn't match, or if no FQDN is returned, it's much more likely that the sending address was spoofed and therefore much more likely that it's unwanted (spam).

What you need to do is talk to the entity responsible for maintaining your public DNS.  This is normally your ISP or an outside service.  It is rare these days for a company to host it's own public DNS.  I bring this point up because there are many administrators who equate the DNS service inside of Windows with the public DNS and that is normally not the case.

What you want in the public DNS is a PTR record.  This associates a public IP address (the one from which your messages make the connection to the recipient system) with a FQDN.  You want the domain name portion of the FQDN to match what your sending SMTP addresses contain (e.g. if your sending addresses follow the convention of name@mydomain.com, your PTR record should contain something like mailserver.mydomain.com).

_____________________________

Regards,

Dean T. Uemura
Microsoft MVP - Exchange (2007-2011)
exchangeguy.blogspot.com
uemurad@yahoo.com

(in reply to itguyme)
Post #: 2
RE: Reverse DNS Failed ! This is a Problem. (report fro... - 8.Feb.2009 1:39:32 AM   
itguyme

 

Posts: 25
Joined: 1.Apr.2006
Status: offline
Thanx a lot uemurad for your answer. I did ask my ISP to add the PTR record and they said that they have added it but still when i go to www.mxtoolbox.com and put my mail server address the error is same.

Kindly tell me what else to do?

(in reply to uemurad)
Post #: 3
RE: Reverse DNS Failed ! This is a Problem. (report fro... - 8.Feb.2009 12:18:17 PM   
uemurad

 

Posts: 8232
Joined: 7.Jan.2004
From: California, USA
Status: offline
First, verify that what they said is true.  Go to any system outside your network (your home computer will work fine if it has an Internet connection).  If it's a Windows-based system, start NSLookup in a command-prompt window.  In it, type the public IP address from which your outbound messages are sent.  If it returns an FQDN that has the proper domain name, it is configured.  If it returns nothing, it is either not set, or hasn't yet replicated out to the public DNS systems.  If it returns something with an improper domain name, inform your ISP and get them to correct it.

_____________________________

Regards,

Dean T. Uemura
Microsoft MVP - Exchange (2007-2011)
exchangeguy.blogspot.com
uemurad@yahoo.com

(in reply to itguyme)
Post #: 4
RE: Reverse DNS Failed ! This is a Problem. (report fro... - 9.Feb.2009 6:19:07 AM   
itguyme

 

Posts: 25
Joined: 1.Apr.2006
Status: offline
ok please let me check and get back ...thanking you for your help.

(in reply to uemurad)
Post #: 5
RE: Reverse DNS Failed ! This is a Problem. (report fro... - 14.Apr.2010 5:04:00 AM   
faraz07

 

Posts: 1
Joined: 14.Apr.2010
Status: offline
same problem here but still no luck. plz advise

(in reply to itguyme)
Post #: 6
RE: Reverse DNS Failed ! This is a Problem. (report fro... - 20.Apr.2010 11:13:33 AM   
MxToolBox

 

Posts: 7
Joined: 1.Oct.2009
From: Austin, TX
Status: offline
itguyme,

I checked out your settings this morning and it does appear that you have the issue resolved as our SMTP Diag is not reporting any issues with your rDNS at this time. Please let us know if we can ever help explain anything or if you have questions.

For more details on the warning rDNS has failed, go here.

Thank you,
@MxToolBox

(in reply to faraz07)
Post #: 7

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