@vmyslivec pointed out that it will be better to suggest users when they want to use their own SMTP server in the maintenance tab that they should use TLS encryption instead StartTLS according to RFC8314.
What I'm not sure is about changes in test together with this line
https://gitlab.labs.nic.cz/turris/foris-controller/blob/a88be0e0c9dea58fec323c93c60c88b556a2895b/foris_controller_backends/router_notifications/__init__.py#L110
If I understand it, when you enable notifications, Foris shows in the importance of notifications as a reboot is required, but in user-notify, there's 0. Shouldn't there be value "1" as it is in Foris? If I'm not mistaken we don't have defined and allowed value 0, because we count that users want at least some notification.
Anyway, this merge requests depends also on this one: https://gitlab.labs.nic.cz/turris/user-notify/merge_requests/3