Last updated on January 16th, 2024 at 03:38 pm

OST files and PST files are the two data files that Outlook uses to preserve users’ email profile data. These files contain all the information of the user’s Outlook profile’s associated data locally.

There are 3 different types of these folders which include options like Personal Address Book (.pab), Personal Storage Table (.pst), and Offline Storage Table (.ost).

Each format handles a different type of data. So basically, it is the directory of all the items in its tree order.

What is OST file?

OST file is an Offline Storage folder available by Microsoft to save the data information and emails when the user is offline or not connected to the internet server.

This file contains the same copy of mailbox data, which is available to the server. You can easily access the data from the OST file in case you are offline or not connected to the server.

If a user uses Office 365, Exchange, IMAP, and accounts in Outlook, they get all their email profile data in this OST file. OST file stores all data locally and automatically synchronizes it to the server on the next connection to the internet server.

Item included in OST file

All items included in the OST file are just the copy of the original data available in the exchange server, this offline folder helps to access the data without a connection to the internet server. When the user comes in contact with the internet, this file is synchronized with the email server and changes are updated. Here is the list of files and folders available in the OST file:-

  • Mailbox data
  1. E-Mail-
  2. Calendar-
  3. Contacts-
  4. Tasks-
  5. Notes
  6. Journal folders
  7. Chats
  8. Appointments
  9. Inbox-Outbox items
  10. Drafts
  • Public folders favorite
  • Shared folders of mailbox linked to exchange server

File location

  1. In Outlook, left-click on the File tab
  2. On the right, look at account settings and click on accounts setting
  3. On the data file tab, click an entry, and click on the open folder location

What is a PST file?

Personal storage table (.pst) is the Microsoft account data that stores the data for the mail accounts and access the information. It helps to maintain the data in the local computer and the user can easily operate and access the information within a limited time and without the internet server.

Also, POP accounts create Outlook items in the system locally as a backup. PST files are used by all versions of MS Outlook 2000, 2003, 2007, and 2010. PST files can easily be compressed by the “Compact now” option available in Outlook data file management.

Items included in the PST file

  • Folders with Outlook items
  1. Emails
  2. Emails attachments
  3. To do items
  4. Appointments
  5. Contacts

The location of the PST file saved by default is:-

  • For Outlook 2007


  • For Outlook 2010 and upper editions

C:\Users\%username%\Documents\Outlook Files

Types of PST files

At present, there are two types of PST file formats which as known as ANSI and Unicode. ANSI is the older version with support for Outlook 2002 and a size limitation of 2 GB. On the other hand, Unicode is the latest format which is workable with all variants of Outlook after Outlook 2002 with a size limit of 20-50 GB (according to the version).

Difference between OST file and PST file

The most basic difference between these two files is the management system of emails. OST file can be created, opened, or backed up independently as it is bound with email account configuration. Whereas PST files can be restored individually very easily.

Also, the OST file handles Office 365, Exchange, IMAP, and Outlook accounts as an offline mailbox. But PST provides support to POP3 accounts with current mailbox items only

Note:- As the data stored in an OST file or PST file is crucial there is an equal chance that these files may corrupt. So try the eSoftTools OST recovery tool or PST recovery software to restore data of the respective file without missing any fragment of information regardless of version, size or corruption of the file.

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