The results of any search are sorted in the order that documents were added to the database. You may sort your documents chronologically, by author, by document type, or by any other field you have in your database to help speed up your review.
When you are sorting, you need to remember that it only affects your current search results.
In order to sort your documents by a field, click on a column heading in Table view. Documents are sorted in ascending order by the selected field. To sort in descending order, click the column heading a second time. You can also sort documents by multiple fields using Sorting Layouts.
After sorting and reviewing your records, you can to refresh the sort order to its original state using the All button on the Toolbar. The All button will quickly return all records to the sort order in which they were added to the database. You can also toggle the All button to switch between your current query or viewing all records in the database.
A Knowledge Based Article on this subject can be found here: How can I make email and attachment families stay together when I sort by email sent date? (cloudnine.com)