Thanks @julian ! 🙂
If I got it right, the plugin nodebb-plugin-category-notifications could solve my issue.
I'd get the result I want if each admin/mod subscribes to all categories, right?
That error message looks very much like TCP port 587 on that IP address is not actually listening for requests. This coudl be firewall related, or that there is no actual service running on that port. Also, for security reasons, please do not expose your IP address in a public forum otherwise it could be open to abuse (not from NodeBB of course or any of it's members, but I think you get the idea).
There was indeed an issue with the firewall as ticked the wrong setting. However now I am struggling with a MFA issue.
Invalid Login ... Authentication unsuccessful, the request did not meet the criteria to be authenticated successfully. Contact your administrator. [FR0P281CA0119.DEUP281.PROD.OUTLOOK.CO