I repeatedly get the following message when I try and collect my Microsoft Outlook for Mac 2011 email on my Macbook Pro 2014 model, with Yosemite OS and all of the latest product updates installed for all software on the machine

The server for account "(Server name removed by poster for privacy)" returned the error "Logon failure: unknown user name or bad password." Your username/password or security settings may be incorrect. Would you like to try re-entering your password?

- Password is correct.
- Password works on my iPhone, Outlook webmail, etc.
- Have tried deleting password saved in Keychain.
- Nothing seems to work.

This is disrupting my business. How do I stop it happening?

Please...

Giles