HC is not allowing to create Mailbox in Exchange Server with name " Service"

The account "Service" is already reserved by security principal or security group in Windows operating systems. So, even if you try to create this user account manually in Exchange Server then it will return error
 
<![CDATA[Active Directory operation failed on domain controllerl. The object 'CN=service,OU=domain.com,OU=Name,OU=Hosting,DC=DCName,DC=local' already exists.]]>
 
 For details please visit following forum posts:
 http://social.technet.microsoft.com/Forums/en-US/exchangesvrgeneral/thread/ef4e0199-bfe8-43ae-9218-2fb97955204e
 http://support.microsoft.com/kb/243330