Symptoms - Relocated Microsoft Exchange Server to new physical location and changed internal IP address schema. Upon bringing the Microsoft Exchange environment back online, ActiveSync devices such as iPhones, Androids, etc... were not able to connect and authenticate to the Microsoft Exchange server and presented various errors, based on those ActiveSync devices.
Fix - In order for an ActiveSync device to work, it requires access to the ExchDAV directory in IIS. Access to that directory is restricted (in IIS) to the IP address of the Microsoft Exchange Server. When you change the IP address of the Microsoft Exchange Server, that IP restriction is not changed automatically. You need to access IIS Admin, right click on ExchDAV and change the IP restriction to the new IP of the Microsft Exchange Server. Restart IIS and this issue will be resolved.
You can test this and other Microsoft Exchange Server connectivity issues using the site below -