OST file and PST file are partly known as Outlook Data file. The information of Outlook like contacts, tasks, appointments, sent items, inbox items is stored in Personal Folder File. 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. The properties and attributes of these items are stored according to the conditions of the Microsoft Outlook Message API (MAPI)

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. It is also sometimes referred to as the Offline Folder File. This file contains the same copy of mailbox data, which is available to the exchange server. You can easily access the data from the OST file in case you are offline or not connected to the server. If you are using Office 365, Exchange, IMAP, and Outlook account the data is automatically stored in the OST file and data gets automatically synchronized to the exchange server on the next connection to the internet server.

Item included in OST file.

All items included in the OST file is just the copy of the original data available in the exchange server, this offline folder help to access the data without the 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. In right, look account settings and click on accounts setting
  3. On data file tab, click an entry, and click on the open folder location

What is 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, 2010. PST file can easily be compressed by “Compact now” option available in Outlook data file management.

Items included in PST file.

  • Mail folders

  • Other items with folders

  1. Emails
  2. Emails attachments
  3. To do items
  4. Appointments
  5. Contacts

Location of PST file saved by default is:-

  • For Outlook 2007


  • For Outlook 2010

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

Types of PST files

At present, there are two types of PST file format which as known as ANSI and Unicode. ANSI is the older version with support to Outlook 2002 and size limitation of 2 GB. On the other hand, Unicode is the latest format which is workable with all variant 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 for independently as it bound with email account configuration. Whereas PST file can be restored individually very easily.

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

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

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