How do I search to see if a Gateway Alias has been taken in GroupWise?
The Gateway Alias is not a true attribute on a user. It is a separate record. As such, you cannot use that attribute in the search criteria. The driver would have to be modified to handle that as a special request. We make it look like an attribute of the user for convenience. This way, you use the user to read, create, or delete a Gateway Alias.
Even if you could search for a Gateway Alias by name, and didn't find one, it doesn't guarantee you will be able to create one with that name. This is because multiple objects and attributes share the "address" name space. Recent versions of GroupWise do not permit collisions between any object names or attribute values that share the "address" name space.
The driver has a special search using "Internet Email Address". Here is an example with a hardcoded value.