Security ‎( show explanation )‎
Select this option if you use Outlook Web App on a public computer. Be sure to sign out when you've finished and close all windows to end your session.

Select this option if you're the only person who uses this computer. Your server will allow a longer period of inactivity before signing you out.
Warning: By selecting this option, you confirm that this computer complies with your organization's security policy.

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