Owncloud 10 E-Mail Notification

We have a OwnCloud - Server Version 10.0.10 an have a temporary Problem with notification for Users.
User can activate the mail notification in the user options. Some users get notifications, others do not. All users have a valid email address. The users are authenticated via active directory

Logs or it didn’t happen. Most of the messages should be at warning level (in case you’re logging at error level). Also check what type of notifications you expect to be sent via email, and if those notifications are “allowed” by the user’s configuration.