Outlook hangs opening meeting .msg files? Fix it now

Quick answer for pros

Open the .msg file with Outlook already running, or disable the Outlook Calendar Peek feature via registry (set DWORD: DisableCalendarPeek to 1 under HKEY_CURRENT_USER\Software\Microsoft\Office\16.0\Outlook\Calendar). That kills the hang.

Why this happens

Outlook 2016 and 2019 have a feature called Calendar Peek. It tries to show a preview of the meeting in the reading pane or when you hover over the .msg file. But when you double-click that .msg file directly (like from a download folder or old email backup), Outlook loads the meeting item in cached mode, and the peek engine trips over itself. It’s not the file being corrupt – it’s Outlook trying to do too much at once. Had a client last month whose entire accounting team hit this after they archived old project invitations to a shared drive. Double-click any .msg with a meeting request, and Outlook sat there spinning for 30 seconds before crashing.

The fix: Disable Calendar Peek

This is the only reliable fix I’ve seen across dozens of machines. No amount of repairing Office or deleting OST files helps – it’s a feature bug.

1. Close Outlook completely.
2. Press Windows key + R, type regedit, hit Enter.
3. Navigate to: HKEY_CURRENT_USER\Software\Microsoft\Office\16.0\Outlook\Calendar. If you’re on Outlook 2016, use 16.0 too – they share the same version number internally. For Outlook 2019, also 16.0. If this key doesn’t exist, right-click the Outlook folder and create a new key named Calendar.
4. In the right pane, right-click, choose New > DWORD (32-bit) Value. Name it DisableCalendarPeek.
5. Double-click that DWORD, set value data to 1, click OK.
6. Close Registry Editor, reopen Outlook, and test by double-clicking any meeting .msg file. It should open instantly.

If you’re on a corporate machine and can’t edit the registry, ask your IT admin to deploy this via Group Policy – same key, same value.

Alternative fixes that sometimes work

If the registry fix doesn’t stick (rare, but happens if you have third-party Outlook add-ins like Zoom or DocuSign), try these in order:

• Open Outlook first, then drag or open the .msg file from inside Outlook. Go to File > Open & Export > Open Outlook Data File, then browse to the .msg. This bypasses the peek engine entirely. It’s a workaround, not a cure.
• Disable hardware graphics acceleration. In Outlook: File > Options > Advanced > Display – check Disable hardware graphics acceleration. This helps if the hang is also causing visual corruption on meeting items. I’ve seen this fix work on two machines with older Intel GPUs.
• Clear the Outlook calendar item cache. Close Outlook, rename the %localappdata%\Microsoft\Outlook\RoamCache folder to RoamCacheOld, restart Outlook. This rebuilds the calendar sync state. Doesn’t always fix the .msg hang, but clears other weirdness.

Prevention tip

Stop double-clicking meeting .msg files from outside Outlook. That’s the trigger. Instead, save the .msg file to a folder, then drag it into an open Outlook calendar view. Or, if you’re emailing meeting invitations, tell your team to open them from inside Outlook’s calendar – not from File Explorer. If you must work with .msg files regularly, disable Calendar Peek proactively on every new machine you set up. It only takes 30 seconds, and it’ll save you the spinning hourglass.

One more thing: if you’re on Outlook 365 (the subscription version), this bug still exists in the Current Channel builds as of early 2025. The same registry fix works there too – just use the same 16.0 key.

Bottom line: it’s not your file, it’s not your computer. It’s Microsoft’s half-baked preview feature. Kill it with a registry edit and move on.