When Outlook for Mac 2011 experiences connectivity issues with Exchange Server, Outlook waits 30 seconds before it tries to contact Exchange again. If it still cannot contact Exchange after 30 seconds, Outlook gradually increases the wait period in 30-second increments until it reaches 5 minutes, or until it successfully receives a response from the Exchange server. If the Exchange server still does not respond to Outlooks requests after the 5-minute wait period, or if Outlook receives an error response, Outlook waits for 5 more minutes and then tries to contact the server again. This process is repeated until the Exchange server responds.
This logic was added to Outlook for Mac 2011 build 14.4.1 to prevent the client from trying to continuously contact the Exchange server when there are connectivity issues. (That behavior can cause network traffic problems.)