What is the difference between deleted and deactivated users?
The difference between a deactivated user and a deleted user is that a deleted user can be anonymized. If you don't use the anonymization function, the two categories are still a great help to keep track of users who have left and are temporarily absent (e.g. parental leave).
Note
Users who are only temporarily absent should be deactivated and not deleted.
Can I delete users from COYO completely?
It is not possible to completely delete users in COYO, i.e. to the extent that they are no longer displayed as deleted in the system. The reason for this is that these users can also be reactivated if necessary.
Important with regard to data protection
For a deleted user, the personal data can be removed via anonymization. You can set this setting in Administration under General Settings > General Settings.
How can deleted users be restored?
Non-anonymous users
Click on the user's menu item in the user administration, then click on Restore and then on Activate again.
Note
As of COYO version 11, a disabled setting looks like this:

Anonymous users
An anonymous user is not recoverable. After the expiration of the period defined by you (by default it is 2 days) the user is irretrievably deleted.
Note
This change is fully implemented from COYO version 11 - please adjust the values for final anonymization according to your company agreement. An anonymous user can't be restored.

Important note for user provisioning by a directory
Note
If the user was provisioned by a user directory, then it must be ensured that the user is active according to LDAP Sync, only then the user is not deleted again.
In the case of anonymization, or if there are problems creating a new user, it is often due to the reuse of referenced user IDs. Anonymous users keep their referenced user ID from the user directory. To create a new, empty user, click on "Edit" in the user administration of the anonymous user and adjust the refID under "Advanced" (e.g. by appending the note "deleted" to the refID).
I have accidentally deleted a user and can no longer use their email address for an account. Is it possible to undo this?
Option #1
You can reactivate the user in the user administration. To do this, set the filter of the user administration to "Show deleted" and restore the user there via "Restore user".
Note
Please note that this is only possible if the user has not been anonymized directly during deletion!
Option #2
Replace the mail address of the deleted user with a dummy mail address. To do so, set the filter of the user administration to "Show deleted" and edit the affected user there by entering a dummy for the mail address, e.g. de@de.de. You can then use the original mail address again.