When we connect Outlook 2007 to Exchange Server, we may receive a variety of errors due to there being no default gateway set on the machine. Please refer to the following article for how to work around this issue.
Error messages when you try to connect Outlook 2007 to Exchange Server: “The action cannot be completed” or “Your Microsoft Exchange Server is unavailable” or “Cannot start Microsoft Office Outlook”
NOTE: Based on our analysis, this issue always occurs when a user tries to connect at home via RPC over HTTP. Since home PC’s ISP may not have default gateway set.