I have various clients using Gmail, Exchange, and other externally hosted email services.
This generally works quite well after setting up custom MX, CNAME, and TXT records but I'm a little unclear of the recommended setup at Jodo and HSphere.
You can do the same with it here if using external hosting for email, disable the email service, and setup custom DNS A, MX, TXT records for them as required in Hsphere.
