This first tab is also a good Outlook Profile PST manager.
You can add multiple pst's at once using shift-select. You can remove PSTs.
Split by date options are Year, Quarter, Month
Split by size will create part1, part2 type files.
The filtering is powerful. Use this if you only want a subset of your mail to be MailScavated.
The default operation is Move (to move messages to the new PST files) but you can also do a Copy or just a Scan (useful if all you want are the stats).
Addresses / Days Stats
If you want MailScavator to collect stats about all the addresses it finds, put a check in the 'Addresses' box. It will display all the unique addresses and days.
When the scan is done, the program logs results into XML files so you can open them in Excel.
More Information about .pst files
Outlook uses .pst files to store all of it's data. Each root-level 'mailbox' on the left side of outlook represents a single .pst file. Right-click -> Properties will show you the location of the .pst file.