How do I temporarily disable an add-in?

You can turn off only add-in which was installed "Only for me". If you used installation type "For all users" you will not be able to turn off an add-in, you will have to uninstall the add-in to turn it off.

Open the list of installed add-ins (menu "Tools \ Options \ Other \ Advanced Options \ COM add-ins" in Microsoft Outlook 2002/2003 or "Help \ Privacy Options \ Add-ins \ COM add-ins \ Go..." in Microsoft Outlook 2007), find the necessary add-in and clear the selection. After you click “OK” and close the Options dialogue box, the plug-in will be unloaded. You can enable it in the same way.

The only exception is MAPILab NNTP for Outlook, which consists of two program modules: the NNTP transport protocol and the add-in. If you have NNTP accounts, it is highly recommended not to disable the add-in, because it can cause the transport that serves the accounts to work incorrectly. You can disable MAPILab NNTP for Outlook if you have no newsgroup accounts.