I can’t fix this one or find information on it anywhere, but – probably due to Outlook 2011′s clever autodetect capabilities – when its within a corporate firewall it takes the local name of the server – not the externally visible OWA address – so when you leave the firewall the server doesn’t resolve.
My only fix at the moment is to keep changing the address manually in the settings. I’ve tried this but it doesn’t work – I’ve also tried configuring the mailbox manually from outside the corporate firewall but that resets once I’m on the office Wifi too.
Any tips from Macheads or Microsofties appreciated. Will keep scouring the forums, too.