Exchange 2007 and Exchange 2013 Coexistence

I am in the researching/planning stage for my upgrade from Exchange 2007 to Exchange 2013. Both at the same location, same forest and same domain. To throw a twist into this scenario we recently changed our name thus I also need to update our domain name from to  

Information that I have found states " You need to create a legacy domain name system (DNS) host name so your legacy Exchange environment (Exchange 2007) and Exchange 2013 can coexist. During coexistence, we recommend creating and using, for example, a host name of "

It seems as though because I am changing our domain name that I could just keep the associated with the Exchange 2007 server and create the new dns entry and point that to the Exchange 2013 server.  

Does this sound correct?
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Amit KumarCommented:

Actually whenever you upgrade any version of exchange to new version, then it is required to publish two mail URLs one is legacy and one is new. Because until you complete migration of all users you will have to use both mail DNS else atleast one of version's exchange users won't be able to access mails.

Things about domain changing, I wanted to know one thing is it you are renaming Active directory domain or just changing your e-mail domain. If it is e-mail domain change then you install Exchange 2013 first then apply new email recipient's e-mail address domain policy on all users with existing domain's SMTP address so atleast mails will start delivering on both domains.
AmitIT ArchitectCommented:
Renaming domain means lot of work. Not only Exchange you might have other servers and application. I might not suggest to perform domain rename. Better you stick to current domain or create new forest and domain and perform cross-forest migration or you can use resource forest concept. Read this:
No this is not correct.  You *have* to use a record named  This also means that you have to use an SSL that includes the and  Now, you can use, but it would just be easier to use the current domain in the long run.

Also starting with Exchange 2010 it is no longer necessary to use a legacy record.

Edit:  My "No this is not correct" comment is meant to answer the author's question, not any comments made by others.

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preshomesAuthor Commented:
I am not NOT renaming our Active Directory domain just the dns entry for how the server will be accessed.

I have already made this server authoritative for our new name and a year ago I switched all my users over to using new email addresses with the new email domain name.

Right now I have internal and public DNS records for and pointing to our Exchange 2007 server.  I also have the internal and public DNS record for pointing to the same Exchange 2007 server but of course since the domain is different you get the SSL error because the name does not match.

The end result would be that I want to move from Exchange 2007 to Exchange 2010 then use the new email domain name to access OWA, autodiscover, Outlook Anywhere, etc...

Would the best way to go about this be to cut over to the new server using the old domain name and then after the migration change everything over to the new email domain name?
AmitIT ArchitectCommented:
If that is the case, You don't need to create anything new. Setup your 2013 server. Once you plan to move user to 2013. First you cutover your service to 2013. Like OWA or Active sync. Just need to point DNS record to 2013. Then you start moving mailboxes to 2013 server. During this migration. Exchange 2013 will automatically redirect to 2007 user. Read this guide:

adding one more KB
preshomesAuthor Commented:
Amit - you are suggesting that I don't need to create the record?


1. Install Exchange 2013 server roles
2. Change firewall to direct SMTP, OWA, ActiveSync connections to new Exchange 2013 server instead of the current 2007 server
3. When email comes in or if someone accesses their mailbox via OWA the users will be directed to the 2007 server until their mailbox is moved to Exchange 2013 mailbox?
AmitIT ArchitectCommented:
Some confusion at my part, you need that legacy url due to authentication issue. Here is a better article:
Amit KumarCommented:
Hi preshomes,

As a part of migration, you will have publish both DNS legacy and new one. Time by time when you will be moving users on new exchange servers so new users will be able to access mails with new URL.

DNS records like this:

Exchange 2007:

Exchange 2013:
Exchange 2013:

As I already stated that if you want to change E-mail domain so apply new recipient e-mail address policy which will contains old and new e-mail addresses (primary SMTP) to avoid any mail loss and also change OWA URL of exchange 2007 to new domain as well so your migration will be error less.

Once you are done with this please follow below mentioned articles to complete migration task:

Exchange 2007 to Exchange 2013 Part1, Part2, Part3, Part4
preshomesAuthor Commented:
Thank you for the information everyone.  I think I am going to just worry with the upgrade first and then once that is complete then I will look at changing the domain name.

Just to make sure I am clear on this...    its perfectly fine for the the and the  point to the same public ip.  I just change my firewall to point to the new Exch2013 server but when the new Ex2013 server gets that communication it proxies it to the Ex2007 server until that persons mailbox is moved to Ex2013?
preshomesAuthor Commented:
I also have a spam filter in front of the Ex2007 server and once it checks for Spam it sends it to my Ex2007 server. Once I change this to the new Ex2013 server will it also proxy that smtp connection and email to the Ex2007 server?
No, they have to point at two different public IP's addresses.  As for the spam filter, you should change it so that it delivers mail to the 2013 server since the 2013 server will eventually be your only mail server.

preshomesAuthor Commented:
If that's the case then it looks like I will have to preform a rapid migration versus a coexistence migration.  My DB's are only a total of 45GB
AmitIT ArchitectCommented:
45GB, you can do it during weekend easily. if you plan everything properly. It should not take 2-3 hours to complete the migration.

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preshomesAuthor Commented:
Yeah... that's what I figure at this point.  Thanks for all your help!
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