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How to Reduce Outlook PST File Size? Complete Solution

Published By Kumar Raj
Aswin Vijayan
Approved By Aswin Vijayan
Published On August 7th, 2023
Reading Time 4 Minutes Reading

Summery: Are you having trouble managing large PST files? You have come to the right page. In this technical article, we will discuss the best way to reduce Outlook PST file size using manual and professional methods. So, keep watching this post for more details.

Every once Outlook Mailbox items grows as for how much data is transferred and other information gets exchanged. Thus every send-and-receive message will ultimately lead to an increase users mailbox size. Users who need to reduce the size at first delete the Mailbox items. Finally, users could see that file size might not decrease as proportional to the number of .pst files deleted. There are several methods to reduce PST file size and the below section is discussed.

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What Happens When Compress Outlook PST File?

When an Outlook PST file reaches its maximum size, it can cause various problems. Therefore, users face various challenges. To reduce the size of PST files, follow these points:

  1. Splitting large PST files can reduce problems like Outlook crashes and slow performance.
  2. Users can simply manage their Outlook mailbox data.
  3. By compressing the Outlook PST file, you can avoid Microsoft Outlook corruption problems.

Steps to Reduce Outlook PST File Size without Data Loss

  1. Download the Tool and install on system.
  2. Upload PST into the software and click Next.
  3. Choose any option: Split by Size, Date, Year, etc.
  4. Click Next to start splitting the PST file.

Manual Ways to Compress PST Files in MS Outlook

MS Outlook data files can be compressed in many ways; here we discuss the most common and safe way to compress PST files in Outlook 2019, 2016, 2013, 2010 and tag all other models. Let’s move to the manual solution first:

Method 1: Compact the PST file using the “Compress Now” Option

  1. Start MS Outlook.
  2. Go to the “Information” tab.
  3. Select Settings >> Account Settings >> Account Settings again.
  4. Select “File” > “Settings“.
  5. Click “Compress Now” in the pop-up window.
  6. Finally, click OK and close the software.

Method 2: Compress PST File using Mailbox Cleanup Tool

  1. Open Outlook and go to the “Documents” tab.
  2. Select “Tools >> Mailbox Cleanup“.

The following options are displayed: View Mailbox Size, Find Old Items, Find Other Items, View Large Items, Clash Sizes, View Clash Sizes, and Remove Clashes. Choose one of them accordingly.

Method 3: Archive Old Outlook Emails in Compressed PST File

  1. Go to File >> Details.
  2. Select Tools >> Clean Up Old Items.
  3. Select the Archive folder and all subfolders, then select the folders you want to keep.
Note: If you want to keep specific folders, you can create multiple Outlook files (.pst) with different locations.

8. To archive items that cannot be archived, select items with the “Automatic Archiving” check box.
9. Finally, click OK to compress the PST file during storage.

Expert Suggested Solution to Reduce Outlook PST File Size

Outlook PST file Splitter is a reliable and trustworthy tool that helps Microsoft users to split and break oversize PST files into smaller parts. This utility splits the Outlook Data File (.pst) based on size, date, sender’s name, and folder. Also, the application splits the PST file and saves them into multiple. Therefore, the PST file size reduction can be made so smoothly.

Download Now Purchase Now

This tool can split PST file into smaller parts with or without Outlook. Many Outlook users face the problem that Outlook data files have reached their maximum size. However, for ANSI or UNICODE file formats, the PST can be split into multiple files ranging from 1 GB to 1 TB. This utility easily splits PST files damaged due to oversizing or other issues.

Working Steps of the Tool

Step 1. Download & run the software.

Split PST Tool

Step 2. Add the PST file & folder and select the destination path.

 Add the PST

Step 3. Select the provided split options.

Split Split PST Options

Step 4. Now, check the summary and click on next to split PST file.

check the summary

Step 5. In the end, the tool started the process of splitting the PST file.

start the process of splitting the PST file

Read More: How to Split PST File by Year?


The above-mentioned content discussed the manual mechanisms. That helps to manage the size of Mailbox items and to reduce Outlook PST file size. However, there are manual methods it won’t be suitable for all users so it is necessary to move into a professional tool. Here the third-party tool is mentioned in the automated solution which does the process by splitting up the mailbox items.