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How To Compress Microsoft Outlook Files?

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james snow
I believe that my mission is to create impact in the world and make people happy through technology.
Large Outlook files lead to various unwanted errors and corruption issues. Furthermore, large outlook files can also make Outlook take longer to start-up, search, navigate, and shut-down. So, In this article, i will discuss a method to make your Outlook faster and better by compressing pst files
Microsoft Outlook is the most used email client all over the world. It has awesome features and an easy GUI makes it a first choice for the individual as well as organizations. It contains Emails, Tasks, Contacts, Notes, and Appointments,  and as well as file attachments. Eventually, as you save and store more and more files within Outlook, your PST file can develop to a quite huge size especially when there are heavy file attachments
So your Outlook data takes up the most space on your computer’s hard drive.
And unfortunately, large outlook files lead to various unwanted errors and corruption issues. Furthermore, a large outlook file can also make Outlook take longer to start-up, search, navigate, and shut-down For reducing the size of Outlook PST file, users have to delete the unwanted items from each folder, but it moves to the Deleted Items folder, which is in the same file. So in order to delete your PST file permanently you must delete the items from the Deleted Items. Attachments with email messages are also one of the main reason for increasing PST file size. It is always annoying when PST file size reaches its threshold limit as those large PST files deteriorate the efficiency of MS Outlook.
In this article, I am going to share an easy and effective method to compress large PST files.
You can compress the PST file using Mailbox Cleanup tool which is already available in MS Outlook.

Procedures to compact a PST file using Mailbox Cleanup tool

  • Open your MS Outlook
  • Go to the Tools
  • Select Mailbox Cleanup, a dialogue box will appear.
  • Click on the “View Mailbox Size”.This will give you the idea of the usage of different sections of your mailbox with their size.
  • Choose Auto Archive option, to move all your old emails to an archive file in your computer
  • Check the size of deleted  PST files by clicking on “View Deleted Item Size” and then you can delete them using “Empty” button.

 Another method to compact PST files.

  • Start Microsoft Outlook
  • Go to the tool  in the menu bar and click on Account Settings”outlook-compress-4.png
  • “Account Settings” screen will appear on your system. Choose Data Files option.
  •  Select your  data file  which you want to compress
  • Just Double Click on the selected  and  click on the Settings
  • Then go to the  “Compact Now”  button to compress your MS Outlook PST file.


In order to make Microsoft Outlook run faster, constant tweaking and optimization are required. Unfortunately, in the Outlook case, you cannot reinstall as the reinstalling bring lots of headaches and your critical data may get lost during the process.
 So In order to make it better and faster, you can manage your Outlook files by compressing or splitting large PST files etc. 
By above steps, one can easily compress their PST files and make their Outlook faster
Author:james snow
LVL 17

Expert Comment

by:Edwin Hoffer

Your article is really very informative and useful as you have elaborated two methods to compress  Outlook PST file i.e. Mailbox Cleanup and Compact PST feature in an easier way.
Now, I would like to share some more ways to compress an Outlook data file, other than these methods.

As you have discussed in your article about Compact now but there is also an Auto Compact feature in Outlook which shrinks the PST file automatically upto 20% of total file size in the background whereas the Compact Now is a foreground process and we can’t access the system after running the Compact Now command. Also, both the process doesn’t shrink the Outlook files completely. So, I would like to share some more methods to reduce PST file size for user’s benefit.

1. 2 GB Truncation Utility
2. Archive PST File
3. Delete unwanted items

To know more about the above solutions in detail, please visit the link:

Thanks & Regards,
Edwin Hoffer

Expert Comment

by:Virat Singh
Hi James,

These manual steps are great but quite lengthy and time consuming.
So can you suggest me some other option through which I can get the job done but in a short period of time.


Author Comment

by:james snow
Hello Singh
In reality, every user first try manual method as no one wants to spend bucks for any software. Still, if you need you can opt for SysInfo PST Compress Tool. It provides seamless compression of PST files in few seconds. The best part of the software is that is very cost-effective and also available with the free version .
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Expert Comment

by:Robinsan Shaw
"These manual steps are great but quite lengthy and time-consuming. So can you suggest me some other option through which I can get the job done but in a short period of time."

Yes, these alternatives are length as well as these methods have limits. You can fix your pst file size problems using & reduce the size of PST file by removing attachments or you can extract attachments and compress them to reduce the Outlook PST File by software called " PST Compress". This tool can smoothly compress your large

Expert Comment

by:bretli walker
There are multiple solutions available on the internet, you can Google this issue. When I Google, I found very simple solution that can easily compress outlook files.

Expert Comment

by:Johanna Davidson
Rather than compressing PST files, another option is to automatically compress each attached file at the time it is attached using ZipMail for Microsoft Outlook (www.smallerfaster.com/optimization-and-acceleration-for-microsoft-email-and-collaboration/zipmail-for-microsoft-outlook/).
MS Office files and Image files are optimized natively. i.e. made smaller without being compressed into Zip files. Thus, the process is really 100% transparent for your recipients who receive standard MS Office files and image files made smaller by ZipMail.
There is no loss in rendering quality.
Example of optimized files can be found here:
MS Office files:
Image Files:

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