Office 365 (Outlook 2011) - Switch between offline/online modes
If you have a lot of work to do, consider going offline to stem the tide of incoming message distractions.
When you switch between working online and offline, all email accounts within your Outlook profile are changed.
- On the Outlook menu, click Work Offline.
The Online Mode toggle on the Tools ribbon shows that you are working offline.
Click the Online Mode toggle to return to Online mode.