Where are Exchange Web Services: ExtendedPropertyDefinition IDs defined?

Question

In researching how to use Exchange Web Services, I see examples like this

Dim PR_DELETED_ON As New ExtendedPropertyDefinition(26255, MapiPropertyType.SystemTime)
Dim PR_SEARCH_KEY As New ExtendedPropertyDefinition(12299, MapiPropertyType.Binary)

That first parameter is an int that represents the property ID. Can anyone give me a pointer to where those ID numbers are defined?

Answer 1

Those are called Microsoft Exchange Property Tags and can be found here

Answer 2

Have a look at Outlook Spy. It can tell you those numbers. There is a screen shot on that site that shows how to get them.