OutlookStatView is a tiny free program which provides a very detailed report on your Outlook accounts.
Normally this scans your default account and displays the following details for everyone who's ever sent you an email: their display name, email address, domain, the total number of incoming and outgoing emails, the total size of incoming and outgoing emails, the average size of incoming and outgoing emails, their first and last message date, and the email client and computer address they used for those first and last messages.
There's also an option to display hourly/ daily/ weekly/ monthly/ yearly summaries, which are just about email traffic in general (the total number and size of any messages you've received).
Any of these can be sorted by clicking a column header, quickly revealing who's sending you the most emails, with the bulkiest attachments, or whatever else you need to know.
OutlookStatView can produce its reports on any Outlook account, in any version of Outlook, and you're able to save them as text or HTML reports for reference later.
OutlookStatView provides a detailed view of your Outlook accounts, and quickly highlights anyone who's hogging more than their share of your Inbox.