To be completed by the original poster:
Custom (Apache 2.4)
Debian 10 (Buster)
Is it possible to use an external mail server for SMTP by providing the credentials to Xibo? I couldn’t find any configuration for it in the admin interface. All the server software we use (Wordpress, Laravel, …) is supporting this and we’d like to avoid setting up a local MTA just for Xibo, which is usually not a good idea.