File created by Microsoft Outlook for Mac, an email application that replaced Microsoft Entourage; stores a category, which can be used for tagging email messages, calendar items, contacts, tasks, and notes; includes the name and color of the category shown in the software.

OLKCATEGORY files are not manually opened and saved by the user. Instead, the program automatically creates them and reads the category data from them. They are saved within the following directory in Mac OS X: [user]/Documents/Microsoft User Data/Office 2011 Identities/Main Identity/Data Records/Signatures/ NOTE: Some default Outlook categories include Family, Friends, Holiday, Personal, and No Category.