How to perform a Restrict that retrieves null values?

[Terry Lindeman]

The following code is supposed to retrieve all messages where Mileage does
not have the value "done".

Set cNewItems = InFolder.Items.Restrict("[Mileage] <> ""done""")

It retrieves messages with Mileage = "", but not messages with Mileage =
NULL. This seems to be a problem with Exchange moret than POP3. In SQL, I
could just say:

select * from message where mileage <> 'done' or mileage is null

Requesting Mileage = "" will get the blank ones, but not the null ones. Is
there a way to request null values in a Restrict clause?

Terry Lindeman