I encountered the same issue shortly after the last MS updates. The message I get when attempting to send is "not implemented". I did a repair with and without the Office Pro 64 disk. The other strange message is "Your mail box is currently being optimized as part of upgrading to Outlook 2013. This one-time process may take more than 15 minutes and performance may be affected while the optimization is in progress" It has now been several days!
I am using in outlook, both my office 365 business email as well as a POP account and have been for years.
I cannot access "add an account" or account access as nothing happens. The strange thing is it is infact syncing up with my other computers and windows 8 phone as I deleted some emails and that in fact synced to my other computers.
I am running Windows 8 Pro and office 2013 both of which were working fine until the Outlook thing reared it's ugly head.
I can still use my Office 365 online so I'm not dead in the water but none of the changes I've made on any of my 4 computers or phone are reflected on this system's Outlook which I thought strange as it did work the other way around.