Lync 2013 installation errors out when you run Forest Prep during coexistence with Lync 2010

During the Active Directory prep portion of the Lync 2013 installation for coexistence with OCS 2007 R2/Lync 2010, I ran into an issue with Step 3: Prepare Current Forest. For those of you that do not know what this step does, it creates the Active Directory global settings and objects and universal groups used by Lync 2013 as well as granting access permissions on the AD objects. Initially not knowing what would happen, I ran thru this step with the default settings:

After clicking Next and it came up with the following error:

This was because it found the existing universal groups from the Lync 2010 installation. Looking at the above mentioned log file, it stated: "Specify  where to create new Lync Server universal groups explicitly at the command line with the GroupDomain parameter." With this being said, I went ahead and ran step 3 once again this time specifying the Domain FQDN as in the example below:

After clicking Next, it completed without errors.

Hope this helps.

Search for specific EUM extensions with Exchange Powershell and EMC

Trying to find extensions that are already assigned to someone in Exchange Unified Messaging can be frustrating if you have never done it before. The easiest way to do it is to perform a search in Mailboxes in the EMC and enter in eum:1234 in the search field.

Another way to do it for the Powershell users is to use this:

Get-mailbox | ? {$_.emailaddresses.eumaddress -like "*1234*"}