Shrink PST: Step-by-Step Guide to Fix PST Storage Issues on Servers by Compressing Files

As PST files on an Outlook server continue to grow, problems arise, such as slow system performance, delayed email loading, increased backup sizes, & frequent storage overflows. Keeping PST files under control is crucial, especially in organizations that receive thousands of emails daily.

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The best solution to these problems is to shrink the PST file, i.e., reduce its size by compressing the PST file. In this blog, we'll explain:

Why PST files grow large

• How to compress PST files manually within Outlook
• Which third-party tool shrinks PST file size in a fast, secure, and server-friendly way?
• How to fix server storage issues with a PST shrink

Main reasons for PST file size growth

PST files gradually grow large because:

• Thousands of emails accumulate in the inbox
• Heavy load of attachments
• Deleted items are not emptied
• Sent items are never cleared
• Old emails are not archived
• Outlook auto-compact is disabled
• Multiple PST files remain on the server

These reasons can cause PST files to reach 20GB, 50GB, or even 100GB+, putting a heavy load on the Outlook server.

Shrink/Compress PST: What are its benefits?

Shrinking a PST file:

• Server space is freed up by 40–80%
• Outlook loading speeds increase
• Corruption risk is reduced
• Backup time is reduced
• Managing PST files is easier
• Server storage costs are also reduced

PART 1: How to shrink a PST file in Outlook using the manual method?

Microsoft Outlook has a built-in option to compress a PST. However, this method is time-consuming and less effective for large PSTs. However, it can be used for small and medium-sized PSTs.

Step-by-Step Manual Method (Outlook Built-in)

Step 1: Open Outlook

Go to Outlook and select the data file you want to shrink.

Step 2: File → Account Settings → Data Files

Here you will see all your PST files.

Step 3: Select the PST file and click Settings

Step 4: Select the “Compact Now” option

Outlook will now compact the PST file.

Note:

This process can take a while.

It only works well if you've emptied Deleted Items/Sent Items.

The impact is minimal for 20GB+ PST files.

Step 5: Restart Outlook

After the shrink is complete, restart Outlook and check the size.

Limitations of the Manual Method

1. Slow on large PSTs (50GB–200GB)
2. Not suitable for server-level PSTs
3. Outlook needs to be kept open constantly
4. Cannot compress attachments
5. Does not work on corrupted or oversized PSTs
6. Cannot compress multiple PSTs in batches

For server systems and large PST file compression, the Manual Method is therefore insufficient.

PART 2: Shrink PSTs Fast & Safely with a Third-Party Tool

Due to the limitations of manual methods, many IT admins and server managers use a dedicated PST compression tool.

DataVare Outlook PST Compact Expert is professional software that safely and seamlessly reduces the size of Outlook PST files. It optimizes the file without altering its contents, improving Outlook performance and significantly saving storage space.

This tool runs smoothly on all Windows & Outlook versions, and it compresses even large PST files without any issues.

Key Benefits: Outlook PST Compact Expert Software?

1. Reduces the size of PST files by 30–70%

The PST file becomes lighter by this tool's clever removal of unnecessary space and compacting.

2. No risk of data loss

The program does not affect the emails, attachments, contacts, tasks, or calendars that are stored within; it merely reduces the size of the file.

3. Easily compresses even large and oversized PST files

Even PST files of 100GB or larger are easily optimized.

4. The tool works whether Outlook is installed or not.

It's a standalone application, so it doesn't require Outlook.

5. Bulk PST compacting feature

If multiple PST files need to be compressed, this tool can compact them all at once.

This is a very useful feature for offices, organizations, and server-level users.

6. User-friendly interface

Even non-technical people can use it easily.

Step-by-Step Guide: How to Compact a PST File with Outlook PST Compact Expert?

Step 1: Install & launch the software.

It is simple to use & has a clean UI.

Step 2: Click Add PST Files.

Single or multiple PST files can be added simultaneously.

Step 3: Choose a Compact Mode.

Several compact options are available to suit your needs:

Remove Unused Space

Compact without Removing Attachments

Extract Attachments to Folder

Remove Duplicate Items

Step 4: Set the Output Location.

Select where you want the shrunken PST file to be saved.

Step 5: Click Start Compacting.

The software will immediately begin compressing the PST file.

Your new, smaller, and optimized PST file will be ready in a few minutes.

If regular PST management is required on the server, a third-party PST compression tool is the safest and most professional option.

After all,

If you're worried about the ever-growing PST storage on your Outlook Server, PST shrinking is the best solution. The manual method is fine for small PSTs, but for server-level or large PST files, using a dedicated PST compression tool is safer, faster, and more effective.

This increases server performance, saves storage space, reduces backup time, and eliminates the risk of PST corruption.