This article may interest you, if when you try to receive email in Outlook for Mac 2011, you receive an authentication fail error message prompt.
You may experience this issue, if you have incorrect account settings.
To resolve this problem, adjust the account seetings. Do the following:
1. Launch Outlook.
2. On the Tools menu, click Accounts.
3. On the left side of the window, select your email account.
4. In the Outgoing server box, enter the correct SMPT server information.
5. Make sure that override the SMTP port is selected. Enter 587 in the box.
6. Close the Window.