Outlook PST reader?

I have too many users with laptops, and their HDs is beeing to be full, they have large .PST files cause they have years of emails.
But whats a solution for backup a .pst and make it available for search/explore, cause microZoft just says: “Copy your file to your disk and change READ-ONLY”

NO, we cant return the big file, thats why im removing it from the hdisk.

Is there another 3rd party utility to read this files?? what to do?