While traveling I could not get Outlook on my laptop to send/receive any emails. The Outlook status bar would say Disconnected and checking the Outlook Send/Receive Progress Errors would show “Task ‘Microsoft Exchange Server’ reported error (0x80040115) : ‘The connection to the Microsoft Exchange Server is unavailable. Outlook must be online or connected to complete this action.’”
I tried everything from ipconfig /flushdns; changing the DNS Server; repairing the mailbox; even reinstalling Outlook. Nothing worked and I felt crippled without email (oddly/luckily I could receive emails on my Windows 7 Phone so I was not completely paralyzed).
The solution? My work PC had Outlook still running but Outlook had crashed! After stopping the crashed Outlook, it starting working again on my laptop.