During the indexing process you might not be able to find all emails or sometimes end up finding partial emails with the following error "No matches found. Search results may be incomplete because items are still being indexed" This might be the reason for incomplete indexing or corrupted index file.
In this case you can rebuild the Outlook Index to fix this:
This will make Outlook to rebuild its entire search index. This can take a while depending on the size of your data file. You can still continue to use Outlook and the indexing will be performed in the background, however, it is recommended not to use Outlook or your computer during indexing to ensure faster operation.
