Log in by following these steps:
1) Open Outlook 2013
2) In the menu bar click Mimecast. From the menu that opens, select Account Settings. The following usr interface will appear:
3) If you have not connected to Mimecast or changed or password these options will saying either failed or missone password. The only authentication method Wixon uses currently is Domain Authentication ( the bottom one). Click the Domain Authentication Edit button. Your Email address will appear. Enter the password used to login to your PC which is also the password used in your Office 365 account login.