Discourse Andere SMTP

I’m glad I found this plugin, as we have issues sending mails to GMail users.
I installed the plugin, but mails to GMail are still not going out. I’m unsure with some options and maybe I misconfigured. I miss documentation about which authentication modes are possible and if SSL/TLS is available. And I’m unsure what to put in " maillist allowing emails"

I tried all three options from E‑Mails über einen Drucker, Scanner oder eine App senden  |  Gmail  |  Google Workspace Help without success. These are my current settings: