Enterprises are more or less concerned with the back end, not the clients. And all of those are clients, and more or less meaningless since a lot of different clients can configured to connect to the back end (in most cases).
If you are looking at Enterprise email for work, meaning an exchange server you will want something that will work with Microsoft Exchanger servers. since that is the most common type that is used. I used Entourouge with a exchange server hosting company and they were using M$ exchange. worked very well.