Configuração SMTP para usar localhost ou 172.17.0.1 não está funcionando, como depurar

[meglio (Anton)]

Acontece que o tráfego precisa ser redirecionado, leia mais aqui:

Use Protonmail Bridge with Discourse

Problem: a) Protonmail Bridge cannot listen to IP other than 127.0.0.1, and b) Discourse in a Docker container cannot send SMTP requests to 127.0.0.1 of the host machine. Solution: We configure it to send to 172.17.0.1 (the Docker’s bridge IP on the host machine), and then redirect to 127.0.0.1, on which the Protonmail Bridge is listening. We do it with using Socat. How To Start by installing Socat: apt install socat We will run Socat as a service. Create service file: nano /etc/systemd/s…