...
The indexing process breaks down emails and attachments to text. This process allows you to receive accurate search results.
To create a project, click the left toolbar button, give your project a name, and then select if you want to index the attachments from that file. You can uncheck the box to skip the indexing of the attachments.
The option to include or exclude the attachments for the indexing process is per project. Excluding the attachments will improve the indexing process, but it will not include search results from the attachments.
...
After you have named your project, you can add emails from a directory or a PST file to that the project for indexing by clicking the right button. See the below image for the location of these functions.
...
After email files are added to your project, indexing automatically begins and continues until completed. Once completed, it will load all your emails and will present them in the viewing pane, or it will move to index the next file in your project.
...