How to debug Email Event Receiver
By namwar - Last updated: Thursday, January 14, 2010 - Save & Share - One Comment
Normally when you debug an event receiver in SharePoint, you attach your debugger with w3wp.exe process. But email received event is not processed by this process.
Instead, you need to attach your debugger with OWSTIMER.exe process. This is the “Windows SharePoint Services Timer” service.
If this process is not listed in your processes list then click on “Show processes from all users” to display all processes similar to following:

Comment from Aaron
Time June 17, 2011 at 8:03 am
Just wanted to drop a quick cheers on this one, spent some time trying to debug, read this and did the “Doh!”