Guide

How to back up Outlook while it's open

Classic Outlook keeps all your email in one big file, and locks it while Outlook is running. That's why so many backups quietly leave it out.

Updated October 2026

Where your email is

Classic Outlook – the one with the File menu – keeps email that isn't on a server in an Outlook data file ending in .pst. On Windows 11 it's usually in:

C:\Users\your name\Documents\Outlook Files

To find yours for certain, in Outlook choose File › Info › Account Settings › Account Settings, open the Data Files tab, pick the file, and click Open File Location.

You may also see files ending in .ost. Those are Outlook's copy of mail that lives on a server (Microsoft 365, Exchange, Outlook.com, Gmail). They only open in the Outlook profile that made them, and Outlook downloads them again if they're lost – so they don't need backing up. The .pst files do: they're often the only copy of old email, archives, and anything set up with POP.

Why backups skip it

While Outlook is open it keeps the .pst file locked, so other programs can't read it. A backup that copies files one by one either skips it or reports an error, and many people only find out when they need it. Leaving Outlook open all day – or in the background – means the file is never backed up at all.

Three ways to back it up

1. Close Outlook, then copy the file

Close Outlook (check it's gone from the system tray too), then copy the .pst file to a USB drive. It works, but it has to be remembered, and it only keeps the latest copy.

2. Export from Outlook

In Outlook, File › Open & Export › Import/Export › Export to a file › Outlook Data File (.pst) makes a copy you can save to a drive. It's slow for big mailboxes and, again, has to be remembered.

3. A backup that takes a snapshot

Windows can take a snapshot of a drive (Volume Shadow Copy): a moment-in-time view in which even files that are open can be read. A backup that copies from the snapshot gets the .pst file while Outlook carries on running. This is the one that keeps working without anyone remembering anything.