For the forum site club.geef-model.nl I have set the mailaddress in settings>general in firstname.lastname@example.org. I have created, using incognito screen, a new user and confirmed it but I still don’t receive a notification mail of it.
I also installed the plugin check email and tested it. I received the following mail:
This test email proves that your WordPress installation at http://club.geef-model.nl can send emails.\n\nSent: Wed, 16 Jan 2019 15:32:08 +0000