That is where Topalt Reports helps you - create Outlook report to find that out. Create email amount report to count emails received during certain time (hours, days, weeks, months).
Main features:
-Is FREE.
-Easy to use for beginners, powerful for advanced users.
-Extracts sender email addresses.
-Can export report to CSV file.
-Generates email amount, bandwidth, sender, recipient reports.
-Generates reports by hour, day, day of week, month.
-Can apply date filter.
-Works with all Outlook versions: 2000, 2002 (XP), 2003, 2007 and 2010 (32 and 64 bit).