The content and emails in the mailboxes are not refreshed, i.e.only the old emails are shown, and new emails are not downloaded to Outlook, even though the status bar stated that the folder is updated.Checking too frequently (either automatically or manually) can cause Outlook to hang on the process and you will not be able to send or receive mail until you restart Outlook.Send immediately when connected is in Tools, Options, Mail Setup tab in Outlook 2007 and older.
When the items in Outlook is mismatched with online version, the cached items may be corrupted.
In Outlook 20, Send Immediately when connected is about halfway down the File, Options, Advanced page.
A link to the Send and Receive dialog is on the Mail Setup tab too.
You can disable the synching or set it to prompt before updating via the Outlook Social Connector options.
Even when you have it disabled, you can still manually initiate a sync for a specific contact.