How to Reduce Size Of OST File In Outlook? Step-by-Step Instructions

Last updated on June 1st, 2021 at 07:12 pm

Are you looking for a way to reduce the size of an OST file in Outlook? Then, this article explains the best practices for organizing large OST mailboxes, preventing OST file corruption, and other issues in Outlook 2019, 2016, 2013, 2010, and earlier.

In most cases, Microsoft Outlook makes a local duplicate of mailbox data, also known as an OST file. Outlook creates this file in Outlook user set his or her account with IMAP or Exchange servers.

It’s useful if you have a slow or non-existent internet connection. Even if your internet connection fails for any reason, you can still read and compose messages, schedule appointments, and add contacts without having to connect to the server.

Instant Solution to Reduce OST file size

Unnecessary emails or other elements are one of the most common causes of huge OST files. Try our automatic eSoftTools OST to PST Converter Software if you need to transfer these items from OST files to another format as a backup right away. This program allows you to easily migrate all mailbox items from all OST files to PST format, as well as split the resulting PST files to reduce their size.


What causes OST files to grow in size?

From when the user configures his account in Outlook, it starts to contain all of the data you’ve generated or received in OST files. Outlook saves all emails (in various folders), attachments, calendar schedules, tasks, contacts, notes, hidden items, and other stuff in a single OST file. When you forget to delete unnecessary data, it exceeds the file storage limit, and corrupts the OST file, causing very serious Outlook problems.

How to reduce the size of an OST file in Outlook? Manually

Compact OST file: User can use this in-built function of Outlook to reduce the size of an OST file. Shrinking the file size may assist improve Outlook performance. Follow the procedures below to compress an OST file.

  1. To begin, open Outlook and select the File option from the Toolbar.
  2. Select the Info option now.
  3. Then select Account Settings>> Account Settings from the drop-down menu.
  4. Select the Data Files tab, and choose the data file OST to compact it then click Settings.
  5. Choose the Advanced tab in the opening dialogue box, then click Outlook Data File Settings.
  6. Press the Compact Now button is the final step in the Outlook Data File Settings dialogue box.

Best Method to Reduce Size Of OST File In Outlook

The manual solution outlined above may appear to be useful, but they are also time-consuming. They have the potential to erase any of the contents in the mailbox if not correctly executed. You can choose the option to convert OST to PST file type and save it locally on the client PC to avoid data loss.


For this, users can use eSoftTools OST to PST Converter Software, which can effectively transfer data while maintaining all attributes. OST to PST Conversion tool is compatible with all versions of MS Outlook up to 2019 (including both Unicode and ANSI editions). In addition, administrators can efficiently split converted PST files and directly migrate OST file data to the Office365 environment.


Due to an over-sized OST file, Outlook and Exchange users face several of the problems, including data accessibility and synchronization. That’s why making the process of Compressing OST Files is necessary. In this blog post we have mentioned the manual process and a reliable OST Converter software for reducing the size of an over-sized OST files.

Post a comment