You are setting an event sink on a particular item, right? What is your code?
If you are tracking events from multiple objects, the rule of thumb is to create your own wrapper class that will contain a pointer to the object raising the event and implement the event handler in the same wrapper class. This way when an event fires, you will know which object raised it.
A sample wrapper (off the top of my head) can look something like
public class MailItemWrapper
{
public MailItem item;
public MailItemWrapper(MailItem OutlookItem)
{
item = OutlookItem;
item.PropertyChange += new System.EventHandler(PropertyChangeHandler);
}
private PropertyChangeHandler(string Name)
{
MessageBox.Show(string.Format("Property named {0} changed on item {1}", name, item.Subject))
}
}