All Exchange accounts are backed up (incrementally) once per day, with full backups performed once per week. The weekly backups are kept for a period of one month. Monthly archives are kept for a period of one year. File restorations are available at an hourly labor charge of $100.00 per hour.
Also, once you delete an email in Outlook Web Access (OWA), it goes into the Outlook Deleted Items folder. Then if you empty that folder, you still have 5 days from that point to recover it from within OWA.