If IIS auto login is enabled on your CRM server, end users may experience a problem whereby they cannot login to the Outlook plugin. When a user tries to login they will get an error saying:
There was an error logging on to the CRM server. The error returned by the server is: ‘Incorrect UserID or Password. Please try again
Users cannot login to the CRM Outlook plugin.
This issue is caused by the configuration of IIS. As part of the configuration for the IIS auto login the Windows Authentication needs to be enabled so that the requests to CRM can use the Windows credentials, however the IIS anonymous authentication needs to be disabled otherwise the Outlook plugin will attempt to use this and thus the login will fail.