I'm having issues with one particular iMac which is running Yosemite and Outook 2011, basically Outlook was working fine with an Exchange account until 12/30/15, no more emails after that date, so I've removed the account and tried to re-configure it, then more problems, it does the autodiscover but it fails with the following messages: "authentication failed, check your account information and try again" followed by another message "mail could not be received at this time. the server for the account ***** 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?" So I'm pulling my hair off, I have tried to rebuilt the identity or to even create a fresh identity but nothing worked. The information entered is completely correct, I have used the same username and password over and over on my PC Outlook, iPhone and OWA browser and it works every time. Please help, not sure where to go from here. The account works just fine on a different MAC.