Microsoft Outlook 2016 crashed on me today.
Close any app that is using this file, and then retry.
You might need to kickstart your system.
Restarting my computer was not an option at the time.
Heres how you’re able to solve the issue.
Select Start > Restart.
Fix 3 Disable Cached Exchange Mode
Now attempt to launch Outlook again.
Hopefully, it works fine now.
This may cause speed issues.
If neither of these fixes work, you might have another computer or program grabbing the OST file.
Makes sure anything that uses Outlook is completely closed on any workstation that may interface with Outlook.
Thanks to Alix Jimenez for Fix 3.
