Host online/offline notification via e-Mail not working.

[chris-fh]

I use hothost via docker-compose.yml and Traefik. It is configured to monitor several webpages. A test message via gmail plugin and the general mail plugin arrive, although it seems notification emails are not triggered, or at least sent when a webpage changes ist status (online/offline). The respective options in the gmail oder the general mail plugin are activated (Notify on host_is_offline). In settings "Host is Down confirmations" was set to default (1) also tried out 0, no notifications so far.

How can I debug this, where may I have made a mistake?