Split PST File into Smaller Parts

How to split a PST file

1. Add your PST or OST file

Point the program at one Outlook data file. It reads the folder tree without Outlook open. A closed or disconnected mailbox works fine too.

2. Pick the folders to include

Folder tree shows on the left with checkboxes. Keep the whole mailbox, or tick only folders you care about.

3. Choose a split mode

Pick your split mode from the four radio options, then set the value beside it. By Size takes a size cap; By Date period takes a period length.

4. Set a destination and run

Choose an output folder and start. Each part lands as its own PST, and a CSV report lists every file with its message count and size.

Why split your Outlook PST

A single overgrown PST is behind most Outlook slowdowns. Splitting it removes the cause instead of working around it.

Stop the freezes and crashes that hit as a PST nears the 2 GB limit.
Cut a heavy archive down so a part fits an email or a cloud upload.
Keep tidy per-year archives for audits, storage rules, or a handover.
Your source file is never touched. Every part is written as a new PST.
It all runs on your PC, so the mail never leaves for a server.

Download for Free

Reduce an oversized PST when Compact no longer helps

Outlook's own Compact Now only reclaims empty space, so once a data file is genuinely full of mail it barely moves the needle. Splitting is the physical fix: the tool carves that one heavy file into several smaller PSTs, each small enough to open quickly and back up on its own.

You keep every message, just spread across parts you name yourself. Point Outlook at the parts you still use day to day and shelve the rest, and the giant file that was slowing everything down is gone for good.

Four ways to split, plus a clean paper trail

Split by size

Set a threshold in MB or GB (1 GB by default), and the tool fills each part up to that cap. It cuts on message boundaries, so an oversized message becomes its own part and never gets split across two files.

Split by date period

Group mail by Year, Month, or Week from the message date. Each period becomes one PST, named like 2023.pst or 2024.pst. Undated items go to their own part instead of getting lost.

Split by folder

Send each top-level folder to its own PST. Inbox, Sent, and any archive folder come out as separate files, and folder hierarchy inside each part stays intact.

Split by sender

Route mail into a PST per sender, handy for a legal hold or a single person's correspondence. Senders with only a few messages are pooled into one others.pst so you do not drown in tiny files.

Exclude Deleted and Junk

Leave the Deleted Items and Junk folders out of the split with one checkbox. The parts you keep then carry only mail worth keeping, not the trash you were going to delete anyway.

CSV summary report

Every run writes a CSV that lists each part, its file name, message count, and size. It is a plain audit trail you can hand to a manager or keep with the backup.

Who splits PST files

IT admins and helpdesk

You inherit oversized mailbox archives and need them broken into parts that open fast and back up without timing out. By Folder and By Size do most of that work.

Legal and compliance

When a request covers one custodian or one year, By Sender and By Date period pull just those messages into their own PST, so nothing extra ends up in the export.

Long-time Outlook users

Years of mail in one file eventually turns slow and risky. Split it into yearly parts and everything stays searchable, while that old giant file stops being a single point of failure.

Split PST File

Languages

File Size

8 Mb

Version

1.0

Last updated on

05/07/26

$ 19.99

🖥️ System Requirements

Windows 11/10/8.1/8/7 (32/64 bit)
Intel i3, AMD Ryzen 5 or above
4 GB of RAM or above
NVIDIA® GeForce® series 8 and 8M, Intel® HD Graphics 2000, Quadro FX 4800, Quadro FX 5600, AMD Radeon™ R600, Mobility Radeon™ HD 4330, Mobility FirePro™ series, Radeon™ R5 M230 or higher graphics card with up-to-date drivers
1280 × 768 screen resolution, 32-bit color
1 GB of free hard disk space or above

🙋 Frequently Asked Questions

❓ How do I split a PST file without Outlook?

You do not need Outlook at all. Install the app, add your data file, and it runs the whole split on its own. This PST splitter software reads Outlook data files directly, so Outlook does not have to be installed or open, and you can even split a mailbox exported from another machine.

❓ Is there a free way to split a PST file?

Outlook itself has no split command, so the free routes are all manual. You create new PST files by hand and drag folders across, which is slow and easy to get wrong on a large mailbox. The program offers a free trial that processes a sample of your mail, so you can check the result before you buy a license.

❓ Can I split a PST file by size?

Yes. By Size is the default mode. You set a cap in MB or GB, and each part is filled up to it. Because the split happens on message boundaries, parts land close to the target rather than exactly on it, and no message is ever split across two files.

❓ How do I split a PST file by year?

Choose By Date period and set the period to Year. Each calendar year becomes one PST, named like 2023.pst and 2024.pst. Pick Month or Week instead if you need finer archives.

❓ Is it safe to split a PST file?

Short answer: yes, because the split is non-destructive. Long answer: the program only reads your source file and writes the parts as separate new PSTs. A bad run costs you nothing but disk space. And since everything runs locally, your mail is never uploaded anywhere.

❓ Why is my Outlook PST file so big and slow?

Years of mail, large attachments, and old ANSI PSTs capped near 2 GB are the usual reasons. Newer Unicode PSTs allow up to 50 GB but get sluggish long before that. Splitting the file into smaller parts is the reliable way to reduce PST file size once compacting no longer helps.

❓ Does splitting change my original PST file?

No. Split PST File treats the source as read-only. It writes new PST parts into the destination folder you choose and leaves the original file byte for byte the same, so you can always go back to it.