Learn how to configure your Proxmox server with SMTP details through the Proxmox web UI, so that it can send email notifications for things like backups failing.
Learn how to configure the root user's email address so that they receive important notifications.
Learn how to whitelist your service's IP addresses in mailcow, in order to speed up SMTP sending.
Learn how to send emails from within a Docker container through the use of MSMTP.