Method for Archiving Mail from Pegasus using Maistore Home:
Create mbx unix folder and container.
Search for mails meeting your criteria (for example from and to dates to select old mails).
Or select mails by date within any folder
Copy mails to the mbx container.
Look in your Pegasus profile folder for that user and Mail. In that folder will see an mbx file with the relevant time and date, (it won't be named as you called it , but there will be an associated pmg file with the same name, the first line of which has your chosen folder name from Pegasus.)
Use Mailstore Home (http://www.mailstore.com/en/mailstore-home-email-archiving.aspx) to archive the mbx file directly, there is no need for any other process. It works a dream and is very fast to search for any given string, (less than 2 seconds on 50.000 mails).
If running Mailstore Home in a network environment you will need to use symbolic links to point at the real location from inside a local folder.
When finished you can delete the same mails from Pegasus and the folders you created.
Done