authenticated SMTP for notifications

[pathia]

Describe the bug

I don't see or understand how authentication for SMTP should work

Steps to reproduce

I get
watchtower | time="2024-09-01T22:05:17+02:00" level=error msg="Failed to send shoutrrr notification" error="error authenticating: 504 5.5.4 Unsupported AUTH mechanism" index=0 notify=no service=smtp
These are my environment variables:
- WATCHTOWER_NOTIFICATION_EMAIL_FROM=[email protected]
- WATCHTOWER_NOTIFICATION_EMAIL_TO=[email protected]
- WATCHTOWER_NOTIFICATION_EMAIL_SERVER=smtp.kpnmail.nl
- WATCHTOWER_NOTIFICATION_EMAIL_SERVER_PORT=587
- WATCHTOWER_NOTIFICATION_EMAIL_SERVER_USER=[email protected]
- WATCHTOWER_NOTIFICATION_EMAIL_SERVER_PASSWORD=mysupersecurepassword

Expected behavior

na

Screenshots

No response

Environment

• Platform
• Architecture
• Docker Version

Your logs

.

Additional context

No response

[github-actions]

Hi there! 👋🏼 As you're new to this repo, we'd like to suggest that you read our code of conduct as well as our contribution guidelines. Thanks a bunch for opening your first issue! 🙏