If you are not sure if your authentication is Single Sign-On or Password Authentication, click PoliteMail > Server Connection. Then click OK in the Server Connection box.
If your screen looks like this, then you are Password Authentication:
If your screen looks like this, then you are Single Sign-On and you must contact your IT department for your credentials. However, you may want to first try to close and restart Outlook. Sometimes that resolves problems with logging in.