[Question] How does Activity work?

So I'm trying to configure hourly updates by E-mail with the Activity app that comes with Owncloud, however even after checking all the boxes in my personal settings it does not send me E-mails for activities of any kind. I have used the test mail in the admin panel to make sure mailing works.

Steps to reproduce
1. Configure what activities to E-mail
2. Do some activities

Expected behaviour
I should get an E-mail with the activities of the last hour.

Actual behaviour
Nothing happens appart from stream updates.

Server configuration
Operating system: Ubuntu 16.04 LTS
Web server: Caddy
Database: 10.0.28-MariaDB
PHP version: PHP 7.0.8
ownCloud version (see ownCloud admin page): 9.1.1
Updated from an older ownCloud or fresh install: No
Special configuration (external storage, external authentication, reverse proxy, server-side-encryption): No

Integrity status for oC9+

No errors have been found.

Email Configuration
ownCloud is capable of sending password reset emails, notifying users of new file shares, changes in files, and activity notifications. Your users configure which notifications they want to receive on their Personal pages.

ownCloud does not contain a full email server, but rather connects to your existing mail server. You must have a functioning mail server for ownCloud to be able to send emails. You may have a mail server on the same machine as ownCloud, or it may be a remote server.

This does not really help me, like I said I tried sending a test mail withouth problems.