We are going to be implementing personal archives for Exchange in our organization. For us to get a good grasp on how much space is needed, we need to get an idea of the age of items that we currently have. Is it possible to have a powershell script that tells me the total size and number of items given certain date ranges of all mailboxes in all databases?

What I'd like to have is the 1) number of items, 2) total size of times (GB) - all grouped by date ranges (Less than 15 days, 15-30 days, 30-60 days, 60-90 days, more than 90). Another possibility would be to have it also grouped by mailbox database