When you upgrade CRM for Outlook, one thing to watch out for is duplicate contacts in Outlook. The reason contacts can get duplicated is that if you use Outlook synchronization for contacts and you remove or reinstall the client, the local synchronization database gets replaced. When you reinstall the client and the synchronization runs, a new copy of your synchronized contacts will be downloaded.

To avoid this happening, try to upgrade in place. In-place upgrades do not break the synchronization, and contacts should not be duplicated. If you are going one version in the upgrade, this is the recommended approach. And consider moving to server synchronization so you won’t have to worry about this for future upgrades.

If you are upgrading across multiple versions, in-place upgrades are not practical, and as a result, you will need to uninstall the Outlook client and install the new version. In this case, duplicate contacts cannot be avoided, and a strategy of remediation is your best course of action.

1. Turn off synchronization in the Outlook client.
2. Move all synchronized contacts to a different folder (you can tell which are synchronized by looking at the icon. It’s the two-headed guy).
3. Uninstall the old version of the Outlook client.
4. Install the new client and synchronize.
5. Once the contacts are re-synchronized, you can delete the old contacts from the folder you moved them to.