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SMTP Reverse DNS Mismatch

Posted on 2014-02-05
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Last Modified: 2014-02-06
Hello All,

I am currently running a Hybrid setup with Office 365 and my on premises Exchange server 2007.
Almost all of our Mailboxes have been migrated to the Office 365 but my MX is still pointing to my On Premises Exchange server 2007.

Today I went to MXtoolbox.com just to check on my status and found out that I have a SMTP Reverse DNS Mismatch which can cause some issues on incoming and outgoing emails to external companies.

The message says: "Warning - Reverse DNS does not match SMTP Banner"

Does this pertains to my PTR record?
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Question by:LuiLui77
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Expert Comment

by:Simon Butler (Sembee)
ID: 39838627
I will give you a much shorter answer.

Ignore that "error".

I have outlined why in my blog here:

http://blog.sembee.co.uk/post/Exchange-2007-and-SMTP-Banner-Tests.aspx

Basically they are connecting to your incoming connector when the SMTP banner only applies to you outbound, which is on the Send Connector.

Simon.
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Expert Comment

by:Jullez
ID: 39838729
Are you having issue with sending emails out?

In my case Comcast emails were bouncing back, not always, but 50% of the time, and creating the PTR record on ISP side resolved the issue.
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Assisted Solution

by:Jullez
Jullez earned 1000 total points
ID: 39839233
Luilui77,

If you don't have any issues sending or receiving, you can ignore it, like Sembee said.

I had to deal with NDR's from Comcast because they didn't do their job properly.


So in case you get an error when sending like "route not found" here is what you can do:


Use this http://remote.12dt.com/ to check your PTR.

 Call your ISP, make sure they created a PTR for you, I had to deal with Comcast the last two days, because they didn't and I just couldn't get  to the right person to explain to them that they need to do it on their side....
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Author Comment

by:LuiLui77
ID: 39839249
Thanks for your responses.

Sembee, great explanation on your blog. Will this be the case with Exchange 2013 as well?

I have another Exchange 2013 in house used for Line of Business applications (different FQDN and domain). This box is running in coexistence with my Exchange server 2007. When I perform a SMTP test I get the same Mismatch message.

If this is not the case, I guess that by changing my receive connector to the same FQDN of my send connector will do.

Tell me what you think.
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Accepted Solution

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Simon Butler (Sembee) earned 1000 total points
ID: 39839317
The same problem occurs with all versions of Exchange 2007 and higher because of the dual connectors (Receive and Send).

If you have multiple Exchange servers then changing the FQDN on the receive connector can cause problems with email flowing between the servers. Microsoft don't actually support changing the FQDN to anything other than blank, NETBIOS or the server's real FQDN.

Simon.
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