I am looking for a formula on how to calculate email retention policy in Exchange 2010. We are currently using an external archiving solution and we can define retention policy within this solution.
Our current database size is 2.5TB
Total mailboxes is 3000 users
Therefore average mailbox in Exchange is about 833MB
If I were to apply a retention policy of 180 days or 90 days. What will be the new total storage size.