Delete all sent items automatically

I have a domain that we use to allow our clients to use scan to email on their scanners. I dont want to store the clients sent mail here, once it is sent I want it deleted and removed from the deleted items folder too. I believe this is possible with a Cron job, but whilst I have used CPanel for a lot of years, I have never used Cron jobs and am not familiar with Linux. Would someone be able to point me in the right direction? Also will I need a Cron job for each mailbox or is is possible to have one that runs through each mailbox and empties the sent and deleted items?