@joseph Okay, it's solved.
It works a bit differently than with Infomaniak, since Infomaniak doesn't allow you to modify outbound firewall rules yourself — for example, you have to open a support ticket to request outbound access to port 25.
With Hetzner, I just had to get used to their setup: I needed to manually open the outbound port on the Hetzner Cloud firewall side. :
https://docs.cloudron.io/security/#cloud-firewall
Outbound ports¶
We recommend leaving all outbound ports open. Some providers like AWS EC2, Google Cloud, Digital Ocean forcefully block outbound port 25 for reducing email spam. The only way around this is to either request your server provider to unblock this port or better to setup an Email relay.
It was a dumb issue hahaha omg I need some sleep.
