Why Outlook PST Files Become Large and How to Manage Them Safely

Outlook PST files store emails, contacts, calendars, and other mailbox data in Outlook. Using these files, users often backup, archive, and migrate their mailbox from one account, computer, or email services provider to another. However, these PST files are highly vulnerable to the risks of data loss and corruption for several reasons, and an unreasonably growing PST file is one of them.

When a PST file becomes oversized, it distorts its internal database structure, making the PST file corrupted and inaccessible. Due to this, Outlook will take longer time to open or load attachments, show issues in sending/ receiving emails, and more. Let’s see how to manage large PST files and the factors that result in an oversized PST file.

What makes a PST file oversized?

As directed by Microsoft Outlook, the recommended size limits for a PST are defined as:

• ANSI (for Outlook 97 to 2002 versions): 2 GB

• Unicode (for Outlook 2003 to 2007): 20 GB

• Unicode (for Outlook 2010 to 2021 and 365): 50 GB

Note: PST files often start experiencing a performance downgrade once they reach the bracket of 10 GB to 20 GB.

Now we will move ahead and explore the major factors that lead to the increase in PST file size.

Accumulation of data

Your mailbox storage is occupied not just with the Inbox emails, there is a lot more to that. Over the years, every single email message, attachment, calendar event, meeting request, or contact list that you create, send, or receive is accumulated directly into the Outlook PST.

• A copy of every sent email is stored with the associated attachment.

• Junk or spam emails that aren't permanently deleted stay within the mailbox.

• Deleted items until removed permanently consume the same space within a PST.

White space in the storage

Upon deleting a data item from the mailbox, its space is occupied by the whitespace rather than adding up to the drive’s storage. Therefore, you need to perform manual or automatic compact operations to reclaim the space.

Nested folders and calendars

Deeply nested folder structure, multiple calendars with so many recurring events and appointments associated with a mailbox, and large contact lists, along with notes and tasks can add up to the size of a PST file.

Large attachments

Emails containing large-sized attachments with high-resolution video files, images, PDFs, and other documents can cause an unexpected increase in the PST file size.

What happens when you have a large PST?

Check out the repercussions of having an extremely large PST in Outlook:

• Outlook might take longer to load or become unresponsive.

• Delays in synchronizing and downloading new email messages.

• Takes longer than expected to find and show searched emails or contacts.

• Repeated crashes of the Outlook application when opened.

• Higher chances of data corruption within the PST file.

• Slow performance of Inbox Repair Tool on an oversized PST.

Checklist to consider before managing PST file size

Before you find out the measures to keep the PST file size in control, here are a few pointers to note:

• Take a comprehensive backup of the entire PST file before you try out anything else.

• Validate that the file you’re working with is PST file only and not an OST file.

• Take inventory of all data, such as attachments, calendars, emails, folder count, etc.

• Try using Classic Outlook until you resolve the issue with the PST.

How to manage large or oversized PST files?

Here is what you can do to avoid unexpected issues and manage large-sized PST files in Outlook:

Method 1: Compact the PST file size

Compress your PST file to eliminate empty spaces left after deleting emails. Follow the steps below:

1. Open Outlook and go to File and select Info.

2. Now click on Account Settings > Account Settings.

3. Click Data Files and select the PST file.

4. Click on Settings and then Compact Now > Ok.

Method 2: Archive older emails

Another solution to manage the file size is archiving old Outlook emails and other mailbox data. Below are the steps to archive data:

1.      In Outlook, go to File > Info > Tools > Clean Up Old Items.

2.      Select the folder you want to archive.

3.      Go to Archive items older than and select a date.

4.      Provide the location to save the archive file and click OK to finish.

These methods will help you manage the size of your PST file using the Outlook application.

Conclusion

With the described methods in the article, you can easily manage your PST file size. However, these methods might have some restrictions, such as no guarantee of data integrity, a high risk of data loss or duplicity, chances of unused whitespace, and more. To overcome these challenges, you should use a professional Outlook PST repair tool that will help you recover inaccessible items from the mailbox.  Moreover, it allows you to split large PST files into smaller files to easily manage and store them safely on your local storage.