I am running into an issue with one of my Outlook PST files that has grown very large over time. It has started affecting performance, and I am worried that if it keeps increasing, it may get corrupted. I want to shrink or reduce the size of this PST file, but without risking any data loss. I have already cleaned up some old emails, but the file size is still quite large. Before I proceed with any steps, I’d like to ask: What are the safest and most effective methods to compress or reduce the size of a large PST file without losing emails or attachments?
(22 November 2025, 01:37 PM)Jamesnoah091 Wrote: [ -> ]I am running into an issue with one of my Outlook PST files that has grown very large over time. It has started affecting performance, and I am worried that if it keeps increasing, it may get corrupted. I want to shrink or reduce the size of this PST file, but without risking any data loss. I have already cleaned up some old emails, but the file size is still quite large. Before I proceed with any steps, I’d like to ask: What are the safest and most effective methods to compress or reduce the size of a large PST file without losing emails or attachments?
Even after deleting emails, Outlook does not automatically shrink the PST.
You must manually compact it.
Steps:
Open Outlook
Go to File → Account Settings → Account Settings
Open the Data Files tab
Select your large PST file
Click Settings
Choose Compact Now
This safely removes empty space and reduces file size without deleting anything.
(22 November 2025, 02:09 PM)michaelbrown Wrote: [ -> ]If your Outlook PST file has become very large and Outlook is becoming slow again and again, then it is necessary to shrink it safely. DataVare Outlook PST Compact Expert Tool is an excellent solution. This tool reduces the size of PST file without any data loss. I have used this software myself and the best thing about it is that it makes the PST lighter by compressing the attachments separately. Apart from this, even heavy PST files get compacted without any error. The interface is also very simple, just select the PST and start the compress process. If you want to improve Outlook performance and are troubled by the problem of oversized PST, then definitely try this tool once. It is safe, fast and 100% reliable.
Blog:- https://www.datavare.com/how/reduce-outlook-pst-files/
If the PST is extremely large (multiple GB), splitting it reduces load on Outlook and prevents corruption.
Steps:
Create a new PST file (File → New Items → More Items → Outlook Data File)
Move older emails (e.g., 2021 and older) into the new PST
Compact both PSTs afterward
This spreads your data across multiple files, keeps Outlook fast, and avoids the risk of one huge file becoming corrupted.