When end users attempt to log in to the spam quarantine, their login fails. Upon inspecting the logs, you notice the following entry:
[AuthenticationManager] ERROR - The user name you have provided is shared by multiple directory entries. DDS error code: 800501
Having more than one DDS configured and enabled with SMG sharing the same entries is not allowed.
To resolve this issue, disable one of the configured DDS on SMG by navigating to Administration > Settings > Directory Integration.