You can manually force X1 to perform an incremental index update by clicking the "Index Now" button, located in the Manual Indexing section of the applicable Tools > Options menu.
Let's start an index update for Outlook:
1. Click on Tools > Options
2. Select Outlook and click "Index Outlook Now"
Please Note: Whether you are running the initial index of your system or an incremental index update, the progress indicator (lower, right-hand corner) will always move from 0% to 100% as X1 completes the required job. The end of the indexing cycle is indicated by the "Last Index update" in the Options menu.