Let me describe how you can get rid of piler enterprise. Piler uses open standards and open format. It stores the archived emails exactly in the same format as they are stored on your mail server, namely EML (RFC-2822 format). No proprietary format. No vendor lock in.
You simply execute “pilerexport -A” command, and it starts dumping lots of eml files, each representing a single email. That’s it. Optionally you may want to add them to a zip file, and digitally sign it. No worries, pilerexport can do it for you automatically.