We are looking at moving Messenger to a different server so it can be
accessible from the outside world on v3.

Currently running 2.2.2 on a box and I'm wondering if I can add my
other server to my Messenger service running v3 keeping my current box
at 2.2.2 and then start moving people to the v3 server, or do I have to
upgrade my 2.2.2 server to 3 beforehand.