Error 400 when setting up SMTP

[Javihache]

Hi,

I am using docker compose to start vaultwarden on Ubuntu 24.04 with the following config.

services:
  bitwarden:
    image: vaultwarden/server:latest
    container_name: vaultwarden
    restart: always
#    ports:
#      - 3012:3012
#      - 1080:80
#      - 1443:443
    environment:
      - ADMIN_TOKEN=${VAULTWARDEN_ADMIN_TOKEN}
      - SIGNUPS_ALLOWED=false
      - WEBSOCKET_ENABLED=true
      - SMTP_HOST=smtp.mail.me.com
      - SMTP_FROM=xxxx@zzz.com
      - SMTP_PORT=587
      - SMTP_USERNAME=xxxx@xxx.com
      - SMTP_PASSWORD=password
      - SMTP_AUTH_MECHANISM=
      - SMTP_SECURITY=force_tls
      - LOG_FILE=/var/log/bitwarden.log
    volumes:
      - ./bw-data:/data
    networks:
      nginx:
    dns:
      - "1.1.1.1"
networks:
  nginx:
    external: true

When I try to send a test e-mail I get: [2024-07-28 22:02:53.489][vaultwarden::mail][ERROR] SMTP error: Connection error: failed to lookup address information: Name or service not known

I am running a Pi Hole using a macvlan network in order to work as DHCP server too.

I can resolve URLs from within the container without an issue and I have network connectivity. However I was still getting that error.

However, in a last effort I tried to type in the IP address resolved for smtp.mail.me.com... I got an SSL error due to the certificates. But once I reverted to smtp.mail.me.com of iCloud's SMTP server, then the test e-mail was sent correctly.

I am not sure if someone else could be able to reproduce this issue, but I'll leave it here in case that it helps someone else.