String 

A Unicode string. 

Integer 

Represented as String in Exchange 2007. 

Nullable 

An attribute which does not have to contain a value. If used without another type a String is indicated. 

Boolean 

A standard Boolean value of "True" or "False". 

Unlimited 

An integer represented as a String, with as a special allowed value the string "Unlimited". 

ByteQuantifiedSize 

An integer size represented as a String with or without a size quantifier. Allowed quantifiers: none, B (default), KB, MB or GB.