If a connection from your computer to the server running Exchange isn't available, Microsoft Office Outlook 2007 switches to Trying to connect or Disconnected.
If the connection is restored, Microsoft Office Outlook 2007 automatically switches back to Connected or Connected (Headers).
If you have wireless access, Outlook could reestablish a connection to the server and switch back to Connected status.
You aren't required to change any setting or restart Outlook.
When a slower connection is selected, only headers are automatically downloaded.
The body and any associated attachments are downloaded only when requested by you, or as necessary for synchronization with personal digital assistants (PDAs), auto archiving, and some client-side rules.
However, you do have the option of manually requesting the update.
If Outlook is stuck in Offline mode, see Work offline in Outlook.