Archiving

We are required by law to archive and store all our emails (received and sent) so that they can be retrieved and searched if necessary. Right now we use Outlook/Exchange and simply archive periodically to a PST file that we store (for each user) on our network. We want to move away from Exchange and use Zoho Mail. Some users will maintain using Outlook as their email client and retrieve emails from Zoho Mail via POP-3. They should then be able to use Outlook to archive. Other users (namely me) would prefer not to use Outlook as the email client and use Zoho Mail directly. Do I have a way to archive or export old emails sent and received into a CSV file (or other file type) and then store locally? How do you suggest I deal with the archiving issues with Zoho?