Outgoing e-mails from SMTP sender are missing a Date header

[pcouy]

🐞 Describe the bug

I'm trying to configure the SMTP sender on my self-hosted ntfy server, with my self-hosted mail server using Docker Mailserver. Mails sent by ntfy get bounced by amavis and are never delivered. The mail server works fine otherwise, and other self-hosted services are able to use it without issues.

💻 Components impacted

ntfy server running with Docker

💡 Screenshots and/or logs

When setting the From field to an address with an inbox, I'm able to get the following error message in the bounce notification

INVALID HEADER

  Missing required header field: "Date"

🔮 Additional context

I'm not familiar with Go but I'll try submitting a PR