When I try to send a message using the form in the frontend, it will show me the confirmation, that the message was send. But it doesn't arrive in my mailbox nor in the form submission of the backend. Would anyone know what to do?

And yes I have added a email recipient.

Thank you!

Userforms relies on the standard PHP mail() implementation so test to see if a simple mail() command works in your environment. You will need to have a mail server setup of course to send the email! or use something like my Postmark mailer module to send emails via Postmark rather than running a mailserver.

https://github.com/fullscreeninteractive/silverstripe-postmarkmailer