How can I tell whether a user has logged on to his or her mailbox?

The Last Logon Time field in Exchange System Manager's (ESM's) Mailboxes view will display the last time that a given mailbox was logged on to; unfortunately, it doesn't necessarily tell you when the person who owns the mailbox last logged on or even if the last logon was by a human. For example, the last log on might be by a system process, antivirus scanner, mailbox backup tool, or PDA synchronization tool. If you want to know whether someone has ever logged on to a mailbox, you can check to see whether that mailbox has folders other than the Inbox (e.g., the Calendar and Contacts folders). Microsoft Outlook Web Access (OWA) and Microsoft Outlook create these folders the first time someone uses either application to log on. If no folders other than the Inbox are present, then no one has logged on to the mailbox.