New account: can not send email

I recently (this week) created a murena account. It all works (except effects of the ongoing service outage) and I can indeed receive mails on my phone and on the webmail interface.

Sending mail however, gives an error. “sender address rejected: not owned by user.

Any idea? Saw a report of this error from back in 2020, so it happened before.

Regain your privacy! Adopt /e/OS the deGoogled mobile OS and online servicesphone

Fixed: I had to provide recovery mail address