At first Outlook just crashed when I Quit. A few days later it refused to open "There is a problem with the office database..." and it offered a rebuild... which fell over on step 4 [-18000] So using MS Database Util I created a new identity, set it to be default. Copied the previous identity folders to the new. Rebuild... which fell over on step 4 [-18000] And so it has gone. No matter what I try. I even copied each database folder over one at a time and rebuilt after each copy. Which had limited success. Contacts, Events, Mail Accounts, Notes and Signatures all now appear in the new identity within Outlook. But add say Folders, and it fails. It may be that Folders relies upon one of the other mail folders (Messages, Message Sources, Message Attachments) but how would I know? Does anyone? It's serious stuff for me - a decade+ of my life hangs in the balance and after 10 years of using MS Windows based products without having a calamity like this I am unimpressed with the OS X offering. Having delved into the file system of Outlook 2011 it reminds me of the un-lamented Outlook Express which had a poor reputation for reliability which I would attribute to having (way fewer) folders and many files containing different parts of the whole. The single .PST file of Windows Outlook hasn't missed a beat on my ancient WinTel box for years. This is a new Mac with new software. I'll dismount (or should that be eject) myself from my horse and see if anyone can offer any sage advice.