ownCloud Activity Plugin reports to non-ownCloud Users


i observe a strange behavior. If a user (with ownCloud access) shares a file/folder to a group, then users (without ownCloud access) get an activity report email from owncloud.

Our ownCloud Environment uses a LDAP Backend for autorisation & authentication.

This seems to happen occasionally, because i tested it with some test accounts/test group and didn't get activity report emails on my accounts without ownCloud access.

But the problem persists because i get mails from users (without ownCloud access), who are complaining about the activity report emails.

Is there any known problem with Activity Email Reports?

How can i trigger Activity Report Emails? (it's a pain to wait 1 hour to get one, need it for debugging)

Do someone else have an idea?

Server configuration
Operating system: RHEL 7.2
Web server: Apache
Database: Postgresql 9.3.13
PHP version: 7.0.16
ownCloud version: 9.1.4