The trusted-client timeout is stored as a DWORD, calibrated in minutes, at:
For public clients, it’s a different value in the same branch:
WEB\OWA\PublicClientTimeout (also a DWORD calibrated in minutes)
The default timeout for trusted clients is 24 hours; the default timeout for public clients is 15 minutes. The PublicClientTimeout value can never be larger than the TrustedClientTimeout value.
If your company policy is exceptionally strict, you can set the public client timeout to a mere five minutes. If you’re confident that only properly authenticated users will be accessing your intranet desktops, you can set the value for trusted clients as high as 43200, or 30 days.
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