If enabled, the Use Search History and Only Search New or Modified E-Mails setting enables you to increase the speed and performance of Identity Finder's search by skipping any E-Mails already searched by Identity Finder that have not been modified since your previous search.
The first time you run a search after you enable this checkbox, a search history database will be created with information about all of the E-Mails that Identity Finder searches. Each additional time you run a search with this checkbox enabled, Identity Finder will skip all messages that have not changed since the previous search as long as they did not contain any Identity Matches. E-Mails found to contain Identity Matches during a search will be searched again on subsequent searches unless you specifically add those messages to the Ignore Identities and Locations list.
If you modify your AnyFind settings or Include Unique Identities then you should Delete your database to ensure that all E-Mails are searched again and a new database is created. Additionally, if you use the Search All Locations for Passwords found in Hidden Web Data setting and new items are added, your unchanged E-Mails will not be searched for this new information unless you delete your databases. Therefore, to always ensure maximum comprehensiveness, you should delete your database on the noted occasions.
To view or change these settings, click the Settings button on the Tools and Options ribbon.