Problem
UCS offers to create new users and send them an invitation email, if the Self-Service App is installed. This way, the Administrator does not need to know about the initial password of the users, but instead a random password is set and the users get an email with a token and the reqeust to set a new password on their own.
It might happen that you use this option, but the users receive no such email. The reasons might be quite diverse, but this article should help to track this down.
Investigation
If you create a new user and choose the option “Invite user via e-mail”, a Listener module called selfservice-invitation will listen to that change and create a trigger file in /var/cache/univention-directory-listener/selfservice-invitation/ with $username.send
Those files are picked up by the service univention-self-service-invitation, which then actually sends the mail. The corresponding logfile is /var/log/univention/management-console-module-passwordreset.log and should contain entries like these:
22.09.20 13:16:42.617 univention-self-service-invitation ( INFO ) : Found trigger for user michael
22.09.20 13:16:42.625 univention-self-service-invitation ( INFO ) : Sending token to michael
22.09.20 13:16:42.779 MODULE ( PROCESS ) : Sent mail with token to address michael@example.org.
By default, the emails are delivered to the postfix MTA on localhost (see also UCRV umc/self-service/passwordreset/email/server).
Email delivery can be tracked in /var/log/mail.log
Solution
In my case, the service univention-self-service-invitation was not running:
systemctl status univention-self-service-invitation.service | grep Active:
Active: inactive (dead) since Tue 2020-09-22 12:21:56 CEST; 40min ago
Restarting the service helped:
systemctl restart univention-self-service-invitation.service
Now the service picked up the trigger files and started sending the mails.