Very helpfull to recover addresses of people you contacted when you've lost somehow your address book. But also for instance a good help for employers, managers, supervisors or system controllers wanting to check what external contacts the employees have.
It looks for the "from" and "to" fields in the selected pst file and returns the according email addresses.
(*) With unprotected we mean "no encryption at all". Pst files protected with a password can not be used in Pst2mail, but also files using the standard compressible encryption (without password) can not be directly read by Pst2mail. There is a workaround though for last case: simply make an additional personal folder in Outlook, force the option "No encryption", and copy the mails from the encrypted to the non-encrypted personal folders!! The resulting pst file can be processed by Pst2mail.