OK, thanks. I found this confusing in the docs too, there it says:
Note that the SMTP server shipped with Tutor by default does not implement TLS.
But gmail is an alternative server/when using gmail, Tutor is client.
The default settings in the docs are not sufficient when using gmail, so you automatically start web searching. Then you see that you need to enable /lesssecureapps in your gmail account and that the port is 587. Then I missed the EMAIL_/SMTP_ difference. I think EdX uses EMAIL_ for SMTP settings by the way.
And I tend to rely on logs too. I’m not sure all of the smtp exim mainlog is in the docker log from --follow. But in the exim log it says, cannot assign requested address. This is from exim on the namshi image, the bash script there could check and print more or the tutor scripts could in my opinion because this message sounds more like a DNS issue.
I needed to look around the docker containers anyway and set up https in the process. Does the Tutor documentation cover all of EdX?