Do we have to sign up for a certain time period (eg. 12 months)?
No, there are no long-term contracts with Managed Exchange. Fees for Managed Exchange are charged per mailbox on a month by month basis, so you can cancel your mailboxes at any time by logging a job and the notice will be effective at the end of the current month. You will need to take steps to save your mailbox data on another server before cancelling your Managed Exchange service.
