We recently had some problems with our old Exchange 2003 server. We are preparing to move to Exchange online in about 60 days. Because the database is acting up, we decided to stand up another Exchange 2003 server and move users to it. We are going to leave the original server also. When we moved a couple of test accounts, we noticed that everything worked except for the unified messaging. We use Unity 5 (it's getting upgraded this year also). We can leave messages from internal extensions, and they show up in email. However, when we try to log into the account from the phone, it says that the message server is unavailable. Also, when we call in from the outside, it doesn't even show up in the email box.
What link between the additional email server and the Unity server am I missing?