Consider this scenario: You have server synchronization enabled in your Microsoft Dynamics CRM production environment. You back up a copy of your _MSCRM database and import in to your development server to create a refreshed development environment.
After you import the organization and update the encryption key, the organization will immediately begin synchronizing with your production Exchange environment. This can cause big issues, such as duplicate contacts and appointments.
To avoid this, when you import your organization, before you update the encryption key, go to settings and disable server synchronization.