Apply Get Outlook filter for multiple categories

i have a requirement to get outlook emails which are not having category as “test”. The filter expression i used in GetOutlook activity is “[Category] <> ‘test’” and this works only if no other category is present in mail. If mail has any other category, then this expression is failing.
it will read mail even if it has category as “test” along with any other category.
Can anyone help me with a filter expression to read mail which is having more than one category and category is not equal to “test”.