Searching through PST Files for specific emails

Hi All

I have been tasked with searching through an Ex Users PST file.

There are a number of criteria being asked, for example:
1) All Emails between the Ex User and Person X
2) All Emails between the Ex User and Person Y
3) All emails between the Ex User, Person X And Person Y talking as a group
4) Emails with the word 'Blah' in it

Is there a better way of searching through this PST file other than the Search options that come with Outlook as even the Advanced Search option does not really offer these search criteria.

Any ideas or thoughts would be greatly appreciated.

Thanks
John.