Why does Outlook suddenly stop attaching files you just edited? Why do draft emails disappear after a crash — even though you clicked Save? Why does your colleague see a 'Temporary File Error' when opening an attachment you sent?
All three point to the same invisible layer: Outlook’s temp folder. It’s not listed anywhere in the interface. It doesn’t show up in File Explorer search by default. And if you’re using Outlook for Mac or Outlook on the web, it behaves completely differently than on Windows.
The Short Version
There is no single 'Open Temp Folder' button in Outlook — because Microsoft never built one. You have to get there manually, and the path changes depending on your OS, Outlook version, and whether you’re working with cached Exchange mode, IMAP, or POP.
| Method | Pros | Cons |
|---|---|---|
| Windows Run Dialog (Win + R) | Fastest for Windows desktop users (Outlook 2016–365) | Fails silently if Outlook isn’t running or if profile uses non-default location |
| Registry lookup (HKEY_CURRENT_USER\Software\Microsoft\Office\x.0\Outlook\Security) | Shows actual folder used *right now*, even if redirected via Group Policy | Requires admin rights on some machines; risky if edited incorrectly |
| File > Options > Advanced > Outlook Data File Settings | No command line or registry needed — safe & GUI-based | Only shows temp folder for PST/OST files, not email attachments or drafts |
| macOS Terminal + Outlook preferences | Works for Outlook for Mac 16.85+; folder persists across restarts | Path changes every time you open a new mailbox; no visual confirmation |
Method 1: Windows Run Dialog (Fastest for Desktop Users)
Press Win + R, type %localappdata%\Microsoft\Outlook\Temp, then hit Enter. That’s it.
This works for Outlook 2016, 2019, and Microsoft 365 on Windows — but only if Outlook is already running. If Outlook hasn’t launched yet, that folder may not exist (it’s created on first use). I’ve seen this trip up even experienced users who rebooted before checking.
Here’s the counterintuitive part: the Temp subfolder inside %localappdata%\Microsoft\Outlook\ is *not* where Outlook stores unsent drafts or embedded images. Those live in %localappdata%\Microsoft\Outlook\Offline Storage Files\ — a separate, hidden structure Outlook uses for cached messages. So if you’re hunting for a missing draft, look there instead.
You can also navigate manually: Open File Explorer → paste %localappdata% into the address bar → go to Microsoft\Outlook\Temp. This folder holds things like: preview thumbnails for PDFs, temporary copies of attachments opened from email, and cached HTML renderings of message bodies.
Method 2: Registry Lookup (Most Accurate for Enterprise Environments)
Open Registry Editor (Win + R → regedit). Navigate to:HKEY_CURRENT_USER\Software\Microsoft\Office\16.0\Outlook\Security
(Replace 16.0 with 15.0 for Outlook 2013, 18.0 for newer M365 builds.)
Look for a string value named TempDir. If it exists, that’s your true temp folder — even if it’s been redirected by IT policy to a network drive or alternate local path.
If it doesn’t exist, Outlook falls back to the default: %localappdata%\Microsoft\Outlook\Temp. This took me three days to figure out originally — our company had redirected TempDir to Z:\OutlookCache\, but no one documented it.
Warning: Do not edit this key unless instructed by your IT team. A typo here can break Outlook startup entirely. And yes — this key is ignored on Outlook for Mac and Outlook on the web.
Method 3: Outlook Preferences on macOS (The Hidden Path)
On Mac, Outlook doesn’t use %localappdata%. Instead, it relies on the system’s ~/Library/Group Containers/UBF8T346G9.Office/Outlook/Outlook 15 Profiles/Main Profile/Data/ directory.
To get there: Open Finder → press Cmd + Shift + G → paste that full path → hit Go.
Inside that folder, look for subfolders named TemporaryItems and TemporaryAttachments. These hold files you double-clicked from emails — but they’re auto-deleted within 24 hours unless you manually save them elsewhere.
Important: Outlook for Mac 16.85+ moved this location again. If you’re on version 16.78 or older, check ~/Library/Caches/com.microsoft.Outlook/ instead. No, Microsoft didn’t announce this change. Yes, it broke several automation scripts we’d built for finance teams.
And here’s what most people miss: Outlook on the web (outlook.office.com) doesn’t use a local temp folder at all. It streams attachments directly in-browser. Any ‘temp’ behavior you see there is handled by your browser cache — not Outlook.
Which Should You Choose?
Pick based on your situation — not your preference.
| Your Situation | Best Method | Why |
|---|---|---|
| You're on Windows, need to recover a file you opened from an email 10 minutes ago | Run Dialog method | Fastest path to Temp; files usually stay there until Outlook closes |
| You manage 200+ Outlook profiles and need to verify temp paths across devices | Registry lookup | Shows exact configured path — critical for compliance audits or migration planning |
| You're troubleshooting why attachments won’t open on Mac | macOS Finder + Group Containers path | That’s where Outlook for Mac actually writes and reads temp files — unlike the Caches folder many assume |
| You're using Outlook on the web and getting 'file unavailable' errors | Browser DevTools → Application → Cache Storage | Outlook Web App uses browser-managed caches — no Outlook-specific temp folder exists |
| You’re writing a script to auto-clean temp files weekly | Registry lookup + PowerShell | Script must read TempDir first — hardcoded paths fail under Group Policy redirects |
| You just lost an unsent draft and panicked | Check %localappdata%\Microsoft\Outlook\Offline Storage Files\ first | Drafts live here — not in Temp. This is the #1 recovery mistake I see. |
