Solved: Troubleshoot the “OST file too large” error in Outlook

Summary: The blog demonstrates all about the OST files, the reasons why OST files become oversized displaying an error “OST file too large or Outlook OST file too big” and the possible manual and automated methods to resolve this issue.

Microsoft Outlook is one of the excellent and most used email clients across the globe because of its prolonged security and better user experience. As users start to increase their email communication, the mailbox data of MS Outlook keep on increasing and it grows heavily in size.

Both the OST and PST files are important for Outlook users as they contain crucial data of the mailbox. Here, the files which are in talks are OST files i.e. Offline Storage Table files which keep on augmenting in volume as large data is being added continuously to the mailbox.

In UNICODE OST format, the file size limit can go up to 50 GB throwing an Outlook ost file too big error. However, in ANSI format, files can extend up to 2 GB. There is also a scenario that if you delete the email file, size won’t reduce as of deleted volume because free spaces get acquired by white spaces.

OST File- An Overview

Offline Storage File is a replica of the Microsoft Exchange mailbox. It is stored on the end-user system when cached exchange mode is enabled. OST stands for Offline Storage Table. OST files store all the work in offline mode and whenever Outlook undergoes online mode, all the information gets updated online. The server gets synced automatically at a regular interval of time.

With the help of OST files, users can work even in offline mode. It also helps to work when the network connection on the server is very slow and weak.

Why is the Outlook ost file too big error Occur?

Offline Storage File contains entire mailbox data which has been gathering since your user account has been created. From then, none of the data has been deleted and OST files have become oversized displaying this particular error. The Outlook ost file too big contains the components such as:

  • Hidden items.
  • Mailbox items like emails, contacts, journals, events, to-do lists, etc.
  • Favorites.
  • Shared folders associated with an additional mailbox or Exchange account.

Issues caused in Outlook due to ost file too big

There are some issues that arise in Outlook due to this ost file is too large error such as:

  • Users are not able to add data in the existing Exchange Server emails.
  • Glitches and pauses in Outlook.
  • Outlook OST emails document becomes inaccessible or ost file not opened.
  • Error during synchronization
  • Cannot fix up synchronization issues between MS Exchange server and OST file.

Fixing Outlook .ost file too large Error by Reducing its size

As the Outlook .ost files get piled up by a consistent gathering of mailbox data, it becomes huge in size and starts creating errors and problems. It becomes a necessary task to fix these errors to ensure the proper functioning of the mailboxes and systems.

Also, with the oversized Outlook email file, Outlook becomes inaccessible and may corrupt the entire data of OST and PST. So, let’s explore the ways to fix these types of issues and resolve the error OST file too large.

Methods to Resolve Outlook OST too Large Error

Compacting Outlook mailbox data by reduce OST file size

The size of the Outlook Emails (.ost) can be reduced using the inbuilt Outlook utility. Follow the below steps to compact the Outlook email file and resolve ost file too large error.

  1. Delete OST file items that you think are not required in the future anymore.
  2. Now, open the folder-list view and click on the folder list icon on the bottom of the navigation table. Alternatively, you can do this using ctrl+6 keys.
  3. Click on the File tab in the Outlook menu bar. Go to Account settings and select Account settings.
  4. Click on Data files in the menu bar. Select the data file you want to compact and click on settings.
  5. Now, a new dialog box will be opened. Click on Advanced Tab and then on Outlook Data File Settings.
  6. In the new dialog box of Outlook data file settings, click Compact Now and then OK.
Disabling all the Add-ins enabled

There might be a possibility that Add-ins disrupt the normal functioning of MS Outlook. So, disabling them would not be a bad idea. Follow the below steps for disabling add-ins and solve ost file issue efficiently.

  1. Open the Outlook. Go to the File menu. From the options, click on Add-ins.
  2. In the Manage option of Add-in which is at the bottom, select the COM Add-ins and hit Go.
  3. Deselect the Add-ins that are not in use and click OK.
Auto Archiving large OST file data

Archiving might be a good alternative as it will help to manage mailbox data and reduce Outlook data file size limit. Due to this, space occupied by OST(s) on the server will be cleared and chances of error outlook .ost file too large would be minimized.

  1. In Outlook, click on the File tab and then cleanup tools. Select the mailbox cleanup option.
  2. Now, you are provided with two options:
  • Move the older mailbox items to an archive folder by clicking the Auto Archive option.
  • Click on Empty for deleting items in deleted items folder.

An Automated Method to Fix Outlook .ost File too Large Error

The above-explained manual methods might be useful to reduce file size limits but are lengthy and tedious. These methods might work for some users but for others, it may not work. Also, if there is large corruption in the Outlook files, there is a high risk of loss of data.

Even if you delete OST files, again they may be corrupted. So, users should convert the OST data to PST format to prevent further corruption of mailbox data. So, to avoid all these situations, it is recommended to use a third-party OST to PST Converter tool to overcome this error.

Final Words

From the above discussion, it is clear that by using manual methods we can reduce the Outlook mailbox size limit. But, the process is quite lengthy, time-consuming, and should be done with utmost care. Otherwise, it may lead to the ost data corruption in Outlook.

To prevent such a scenario, users can use OST to PST converter tool to successfully convert the OST data into PST file format. It is one of the authentic and reliable solutions for the conversion of OST to PST. Hence, by using OST to PST converter, we can resolve the “OST file too large” error

About The Author:

Mithilesh Tata is an Email Migration and Data Recovery Expert. He has a keen interest in Technology & Entrepreneurship. Also, he loves cricket, music, and books.


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