email file location in SBS

I'm using SBS 4.5. I have several workstations connected. They are all using Exchange & Outlook for email, calendar, etc. They can view each others calendars, send internal or external email, etc. What I want to know is where and in what file isall of that email and calendar information kept on my SBS. Is everyone's email and calendar in the same file? or is there a separate file written for each user?