Find email addresses in Exchange 2010

The quickest and easiest way to work out who (or what) is using an email address is to open up a PowerShell command window and run: 


get-recipient -results unlimited | where {$_.emailaddresses -match "address@company.com"} | select name,emailaddresses,recipienttype


for full details on the result, try 


get-recipient -results unlimited | where {$_.emailaddresses -match " address@company.com "} | fl