A new feature in UCS is “blocklists” for the Univention Directory Manager (UDM). This feature allows UDM to block previously used values for specific attributes. One possible use case would be preventing the unintentional reuse of an email address, which could potentially lead to one user accessing another user’s emails: a user had the email address “[email protected],” then leaves the company, and their account is deleted. Shortly after, a new user “smith” is created. Now, UDM can prevent the creation because “[email protected]” would be used as the email address again. Blocking old email addresses occurs automatically when the feature is activated (it is initially deactivated) and the corresponding blocklists are created. The blocklists can also be managed with a UMC module.