We have our email/website with the same host.
I have configured an exchange server and have it functioning as a test with https/rpc for another domain that own.
We now are ready to bring the email in from the host (they are still going to host website for now) and control on our exchange server.
From my understanding all I will have to do is have the host do a redirect on their MX record to point to our Exchange server and this will take care of any loss gap issues that will occur while the new DNS is replicated via our ISP.
Also, are there any issues that I might incurr by not hosting the website but hosting the email?