Just for clarification, are you saying that you have successfully gone through the standard install and have a working Discourse instance on arm, however setting up mail-receiver specifically is failing?
What are the errors that you are seeing? If you can provide the error messages, that may help identify a cause. Be careful to check for anything sensitive that needs redacting.
It’s a bit hard (for me) to give it a particular term in relation to Discourse. Under the hood it’s just a totally separate container application for a receive-only email server which happens to be (is deliberately) set up to deliver those emails to Discourse via its API.