OLK File Format

Discover In Detail What Is OLK File And Its Types

Users globally are familiar with Microsoft range of applications and all productivity tools that it has to offer. We have all majorly used Windows Operating System preconfigure on machines. Therefore, the familiarity of the brand is long before and is continued until present. Outlook has consistently been one of its most successful applications serving business communication.

Desktop communication evolved with the introduction of Microsoft Outlook. Apart from the various options that it features, the application is built in a variety of versions. With the variety of versions, you get widespread accessibility of the application and its services.

What is OLK file of Microsoft Outlook and Its Data Types

Data types or data files are the storages maintained by application to store their information. This storage can consist either of configuration details or even the profile contents. Microsoft Outlook is built to generate the following types of data files:-

Windows OS

PST: This is the primary data file type featured by Outlook. When used individually, Outlook creates its default storage in the form of a Personal Storage Table file, i.e. a PST file. This file is built in a binary structure and consists of all the data exchanged or generated using the corresponding profile - emails, address book, calendar (events, anniversary, meetings), tasks, journals, and notes (RSS Feeds - optional). This data file is a proprietary of Outlook and can only be read by the respective application and no other.

OST: This is a cache copy of the Exchange profile. When working under an Exchange Server environment, configuring Outlook in Exchange cache mode generates an Offline Storage Table file, i.e. OST file. This file is meant for offline usage, i.e. when not in connection with the server. Automatic synchronization takes place as soon as the profile is connected with the Exchange environment. The file again is a proprietary and a dependent on the origin Exchange profile plus environment.

Mac OS

OLM: This is the data file generated by Outlook 2011 for Mac OS. The application functions same as its Windows counterpart. However, instead of a PST or OST, this client stores its data in an Outlook for Mac OLK file format, i.e. OLM file. This file is not created by default but has to be generated using the means of export featured by the client. This data file is also a proprietary of Outlook 2011 for Mac and can only be access / read by the respective application.

Additional Storage Maintenance by Outlook

Apart from these described file types, Microsoft Outlook is capable of storing data in different forms. These additional data types are generally the temporary copy of existing contents that help in regenerating the storage just in case of any mishap by the available means.

Outlook 2011 for Mac is the one that maintains profile data storage additionally, apart from the OLM.

1. Database File: The application maintains its profile contents in a database file on the backed storage. This database file consists of complete data stored, maintained, exchanged, or even deleted by the profile. Using Database Utility program provided as inbuilt, users can rebuild a profile in the case of - data deletion or profile corruption.

2. Temporary File: Temporary files are maintained by the profile in the form of OLK. The OLK extension based files are used for individually maintaining the data of a respective profile. OLK14 files are stored in the Identity folder of the corresponding profile to which it belongs. OLK file belong to multiple components of the profile and are not restricted to just storing a temporary copy of messages.

The Outlook 2011 for Mac client was released as part of the MS Office Suite 2011 version, which was introduced exclusively for Mac OS. The client uses the backend OLK14 MESSAGE file for when a message is read on the client end by the user. The OLK file format only stores the corresponding message header data (only).

Besides this, there is another file namely OLK14 MSGSOURCE which consists of the email message contents without the attachment (if any).

NOTE: Attachments are stored separately in another OLK file format.


OLK Folder: this is a temporary folder created on Windows Operating Systems by Microsoft Outlook client. This folder is where all the temporary attachments are saved by the client of the representing user profile emails. There are no OLK15 files generated on Windows by Outlook. As the name suggests, this folder consists of temporarily saved copies of attachment. However, in some of the cases the attachments don’t reside in the folder for a temporary duration but stay there until you delete them purposely.

Default OLK Folder Location

MAC Outlook 2016

/ Users // Library / Group Containers / UBF8T346G9.Office / Outlook / Outlook 15 Profiles / Main Profile

MAC Outlook 2011

/Users/username/Documents/Microsoft User Data/Office 2011 Identities/

What is OLK File format Variants of Mac Outlook

Until now, we only concentrated on the message storing OLK14 file and message header storing OLKs too. However, there is not just one, two, but many OLK files produced by Outlook for Mac client version.

The messages are further divided into multiple components all of which are saved with unique extensions of OLK. The different variants of OLK file extension are listed below which can be read and used to extract data from OLK files.

Category is used for tagging messages, contacts, calendars, or such components. The file consists of name & color assigned to the category. OLK file format cannot be opened or saved by the user. This is an application generated and readable file only for reading the category. Some of the default categories are; Family, Personal, No Category, Holiday, etc.


[user]/Documents/Microsoft User Data/Office 2011 Identities/Main Identity/Data Records/Signatures/

Category File

This OLK file extension is meant to store data of the event(s) created using Outlook calendar. An event like this may consist of the following information; time, date, invitees. Calendar event OLK15 is used for storing local cache of copy of the created events even in the cases where the calendar is stored remotely.


[user]/Documents/Microsoft User Data/Office 2011 Identities/Main Identity/Data Records/Events/

Calendar File

The OLK files for contact stores information related to a contact with details such as; email address, name and business information. This information is entered on the Outlook UI and is used for saving a contact. No direct interaction is made by users after OLK14CONTACT is generated by Outlook.


[user]/Documents/Microsoft User Data/Office 2011 Identities/Main Identity/Data Records/Contacts/

Contact File

The OLK14 MSGSOURCE file consist of the source data of an email for referencing a message. The Application loads this file while viewing a specified message. When the focus is on reading a particular email then the data from the OLK14MSGSOURCE file is automatically loaded by the application. Storing message and its source separately make the client function efficiently.


[user]/Documents/Microsoft User Data/Office 2011 Identities/Main Identity/Data Records/Messages Source

Email Message

The group OLK file by Outlook 2011 for Mac is generated for storing the grouped contacts in a collection. This is done for maintaining collection of contacts in an organized way by the client.

OLK14 MESSAGE file or the message file Outlook 2011 for Mac is only meant to store the header related information. The application uses this file to read the message details, i.e. the header data and not the mail body data. Message overview can be taken on the application frontend by users, with this file loaded by the client on the backend. These files can be read in fragments (of text) using Apple based text editor.


[user]/Documents/Microsoft User Data/Office 2011 Identities/Main Identity/Data Records/Messages/

Message File

OLK file format for signatures is a file that stores email signature of Outlook for Mac OLK file format profile in HTML code form. Thus OLK file is saved and automatically loaded by the Outlook client is inaccessible by users via direct means.


[user]/Documents/Microsoft User Data/Office 2011 Identities/Main Identity/Data Records/Signatures/

Signature File

The contents stored by this OLK file extension consist of account settings of the configured profile, connection, and login details. The file is meant for the storage of account related information, which permits users to get their emails and perform calendar synchronization.


[user]/Documents/Microsoft User Data/Office 2011 Identities/Main Identity/Data Records/Mail Accounts/

Mail Account

OLK14 PREF files are meant for the storage of software related preferences that specify the settings for reading or composing messages. Being application generated and readable files, these OLKs are again inaccessible to software.


[user]/Documents/Microsoft User Data/Office 2011 Identities/Main Identity/Data Records/Preferences/

Mail Account

OLK file for Note storage consists of a Note that was created with the help of Notes component provided in Outlook. Besides storing the note written by user, the file also stores formatting of the Note and is used for Personal and Business notes generated by the user.

NOTE: Being generated in binary formatting too, these files contain a few fragments in text formatting. This makes OLk File readable partially using text editors.


[user]/Documents/Microsoft User Data/Office 2011 Identities/Main Identity/Data Records/Messages/

The OLK files generated for Task contains the ‘To-do’ created by the user on the application. This information represents the marking applied on messages flagged for the purpose of follow-up. The OLK14 TASK is auto-generated as soon as a new task is assigned by the user.


This page is designed to aware users about What is OLK file format? These files are the backend database files maintained by Outlook 2011 for Mac. The OLK14 file works on a database and not a data file as its Windows counterparts. Therefore, the database requires files to support reading contents when the user commands the application for performing a certain functions such as read - emails, notes, calendar, etc. What is OLK file format variants and how they are linked to the other file by the means of file structure in which they are saved. Along with this, the database file, which is situated in the Main Identity folder, is also used for the purpose. There are great benefits of having these OLK15 file besides the database. Relocating or removing any of these OLK15 messages does not cause any blunder, as rebuilding the database will rearrange these files at their respective folders.