You’re about to present to leadership in 90 seconds. You open Outlook — and it freezes for 17 seconds. Then it crashes. You restart. Same thing. Your laptop fans scream. You need clean, fast Outlook *now*, not a troubleshooting rabbit hole.
Most Common Cause
Outlook isn’t holding onto your emails. It’s holding onto
its own memory of them — cached Exchange mode files, autocomplete lists, offline address books, and old OST/PST backups buried in hidden folders. The quick fix? Clear the cache — but not the way most people try.
The beauty of this approach is that it targets only what Outlook actually needs to rebuild: temporary sync state, not your mail or contacts. And it works whether you’re on a shared laptop or your personal device.
Diagnostic Steps
First, determine what kind of ‘data’ you’re trying to delete. That changes everything.
Ask yourself:
- Do you want to remove all local copies (e.g., before handing off a company laptop)?
- Are you trying to fix sync errors or startup hangs?
- Did you accidentally import an old PST and now see duplicate folders?
- Is Outlook Web behaving differently than desktop Outlook — suggesting server-side vs local residue?
If your issue is slowness or corruption, clearing the cache (Fix #1) usually solves it. If you’re prepping a device for reuse, you’ll need full profile removal (Fix #2). If you’ve imported legacy archives and want them gone *permanently*, that’s Fix #3.
Fix #1: Clear Outlook Cache (How to Clear Outlook Data)
This is what most people mean when they search “how to clear outlook data.” It’s fast, safe, and non-destructive.
In Outlook desktop (any version), go to
File > Account Settings > Account Settings…. Select your account >
Change > More Settings > Advanced > Offline Folder File Settings. Click
Disable Offline Use, then OK through all dialogs. Restart Outlook.
Now re-enable offline use: same path, but click
Rebuild next to the OST file location. Outlook will download fresh copies from the server — and discard the corrupted or bloated local cache.
💡 Counterintuitive tip: Don’t click “Delete Offline Folder File” unless you’re certain. Outlook won’t warn you — it just erases the OST without confirmation. And if your mailbox is >10 GB, rebuilding can take 45+ minutes over Wi-Fi. Do this on Ethernet.
Keyboard shortcut: Press
Ctrl+Shift+Esc to open Task Manager, then end any lingering
OUTLOOK.EXE processes before restarting.
Fix #2: Remove Entire Outlook Profile (How to Delete All Outlook Data)
This answers “how to delete all outlook data” — meaning every trace: accounts, signatures, rules, cached credentials, even AutoComplete suggestions.
On Windows, open
Control Panel > Mail (Microsoft Outlook) > Show Profiles. Select your profile >
Remove. Confirm. That’s it.
But here’s what most people miss: Removing the profile doesn’t delete your PST files. They stay in
%USERPROFILE%\Documents\Outlook Files\ or wherever you saved them. To fully delete all data, manually delete those .pst files *after* removing the profile.
Outlook 365 and 2019 store profiles in
HKEY_CURRENT_USER\Software\Microsoft\Windows NT\CurrentVersion\Windows Messaging Subsystem\Profiles. Outlook 2016 uses the same registry path — but editing it directly is risky. Stick to Control Panel.
For Outlook Web users: There’s no local profile to delete. But your browser cache holds auto-filled addresses, recent searches, and session tokens. Clear cookies for
outlook.office.com — not just general browsing history.
Fix #3: Purge Imported PSTs and Orphaned Folders (How to Delete Data From Outlook)
This covers “how to delete data from outlook” when you’ve imported archives or migrated from another email client.
Open Outlook >
File > Open & Export > Import/Export > Import from another program or file > Outlook Data File (.pst). You’ll see a list of all attached PSTs — including ones you forgot about.
Right-click any PST in the folder pane (left navigation) >
Close "Archive". That unloads it — but doesn’t delete it.
To delete permanently: Go to
File > Account Settings > Account Settings… > Data Files. Select the PST >
Remove. Outlook warns you this won’t delete the file — just detach it.
Then navigate to its location (shown in the same dialog), and delete the .pst file manually.
⚠️ Warning: If you used “Import” instead of “Open,” Outlook copied messages into your main mailbox. In that case, you must delete them manually — or run a search:
Ctrl+Shift+F, set “From” to “noreply@company.com” or “Sarah Chen (VP Marketing)”, and delete in batches.
Still Not Working?
If Outlook still lags, crashes, or shows ghost folders after all three fixes:
- Run
outlook.exe /cleanreminders and outlook.exe /cleanfreebusy from Command Prompt (Admin).
- Check Add-ins: File > Options > Add-ins > Manage COM Add-ins > Go… — disable all, restart.
- Try Safe Mode: Win + R, type
outlook.exe /safe.
If none work, your OST may be unrecoverable. Contact IT with this info: Outlook version, Windows build number (
Win+R > winver), and whether the issue occurs in Outlook Web too. They’ll likely rebuild your profile remotely — or push a new mailbox policy.
| Action |
Outlook 365 |
Outlook 2019 |
Outlook 2016 |
Outlook Web |
| Clear OST cache |
✓ Full support |
✓ Full support |
✓ Full support |
N/A |
| Delete PST file via Data Files tab |
✓ (v2308+) |
✓ |
✓ |
N/A |
| Remove AutoComplete cache |
File > Options > Mail > Empty Auto-Complete List |
Same path |
Same path |
Clear browser autocomplete for outlook.office.com |
| Purge sent items older than 90 days |
Auto-expire rules in Rules > Manage Rules & Alerts |
Manual rule only |
Manual rule only |
Not supported |
| Reset entire profile |
Control Panel > Mail → Remove |
Same |
Same |
N/A |
