Public DNS Exchange 2007/2013 Coexistence

What should the public DNS be setup as for Exchange 2007/2013 coexistence.  I may be over thinking this but, do I adjust my firewall to point the existing IP to my EXCH2013?  I'm confused at this point.  I'm not sure how the additional public IP I setup comes into play.  currently I have,, pointing to my Exchange 2007 server.  I added an IP for pointing to Exchange 2013.  I don't plan on using the name newmail but wanted it up there so I could have a placeholder.  I just don't understand how the new IP would come into play.  I would think I just adjust my firewall to point to my 2013 server.

Example of my public DNS: - - - -

New setup? - - -
ZeeIT ManagerAsked:
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Jose Gabriel Ortega CastroEE Rookie/Solution Guide/Topic Advisor and CEO Faru Bonon ITCommented:
HI Zee.
well you have your exchange server 2013, that's the latest version of exchange server.

So you already installed it, so just configure it.

So all your entry points should be pointed to your latest version of Exchange as a general rule.

So don't overthink and the Coexistence of the Exchange will take care of the communication between them.

If you don't plan to use
you'd need to adjust the internal URLs on 2007 to match (
and use on your exchange server 2013 the one that you want to use as final.
Point and to exchange 2013 internally and externally - 1st public IP
Point legacy url to 2007 internally and externally - 2nd public IP
Exchange 2013 redirect traffic to 2007 url (legacy) when mailbox is on 2007 server
MASEE Solution Guide - Technical Dept HeadCommented:
Here is a detailed article from Microsoft Technet.

You can use this to configure your Exchange2013 URLs and certificate.

Use this to generate command for CSR. Refer Above article for the name requirements.

As commented above after configuring all these point common name and autodiscover to 2013.
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ZeeIT ManagerAuthor Commented:
Thank you Jose, but I've already used that article to do my installation along with various other sites.  I'm all set with everything except for the cert and external dns.
ZeeIT ManagerAuthor Commented:
Mahesh, thank you for this info.  I'm sorry if you answered this in your comment but should I change my to the IP address?  Then set to the IP I set for newmail and then adjust my firewall?
ZeeIT ManagerAuthor Commented:
MAS, thank you. I've seen both of the first 2 articles and already have my URLs all setup.  All I need is to understand/setup my external IPs.  I'm lost as to how the new external IP comes into play. I'm beginning to think I just adjust my firewall and set legacy to IP.
ZeeIT ManagerAuthor Commented:
Ok, so I just adjusted my public DNS. > Exchange 13 > Exchange 13 Exchange > 07

I thought it would be easier to go at this from the firewall route but may be overthinking it.  So I went the public DNS route...
MASEE Solution Guide - Technical Dept HeadCommented:
Above is correct.
1. Configure URLs in Exchange 2007.
2. Point your to exchange 2007 (internal DNS and external DNS).
3. Point your (common name) to exchange 2013 (internal DNS and external DNS).
4. Point your (common name) to exchange 2013 (internal DNS and external DNS).

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ZeeIT ManagerAuthor Commented:
Thank you for confirming MAS.  Thank you all for responding so quickly.  I just tested my changes and I am all set.
MASEE Solution Guide - Technical Dept HeadCommented:
Glad to know we could help. :))
ZeeIT ManagerAuthor Commented:
After my changes mail was getting stuck in my 2013 queue.  Turns out I had to create a receive connector to allow the internal relaying to happened.  Not sure how I missed that but I'm not seeing it in the steps outlined by Microsoft for 2013/2007 coexistence.

In case anyone else runs into this problem.  I'm all set now with the 2 servers running and mail flowing.  Time to relax and BBQ, lol.
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