Automatic archiving (AutoArchive) is enabled in two stages. First, you set the global settings for archiving, and then you set custom settings for any folder whose default settings are not what you want.
To display the AutoArchive global settings, select Tools, Options, select the Other tab, and then click the AutoArchive button.
You can also display the AutoArchive global settings by right-clicking any folder (except Contacts) in the Navigation Pane and selecting Properties, selecting the AutoArchive tab, and then clicking on the Default Archive Settings button. The folder must be enabled for AutoArchiving for the Default Archive Settings button to be enabled.
The global AutoArchive settings ...