Your Making Music Platform comes with a fully functional email system, because the Making Music Platform website sits on top of an industry-standard website/email hosting account. The email component of your hosting account - the part of your account responsible for delivering emails to and from your group's email addresses - is entirely separate from the Making Music Platform software itself. But the two systems (your Making Music Platform software and your email service) are nicely integrated. There are pages in your Making Music Platform that allow you to create email addresses - and when you do so, the Making Music Platform software communicates with the email service, instructing it to create the actual email address on the server.
In other words, there are the actual email addresses on the server, and then there's the knowledge that your Making Music Platform software retains about those email addresses. Hopefully those two systems will correspond 100%, where every email address that your Making Music Platform software believes should exist actually exists. But they can become out of sync sometimes. It's possible to manually create email addresses directly on the server that Making Music Platform doesn't know about, and it's also possible that the communications between the Making Music Platform software and the underlying hosting account could break down occasionally.
So it's possible for the actual email addresses on the server to not match what the Making Music Platform software thinks should be on the server.
There is an administration page in your Making Music Platform that compares what's actually on the server with what Making Music Platform thinks should be on the server, and identifies any discrepancies. This is the Email Addresses and Mailing Lists page. There's a link to this page in the Administration Dashboard in your Making Music Platform (on the Emails row).
This page lists all email addresses in your account (both regular email addresses and mailing lists). It lists what email addresses actually exist on the server, and also lists what Making Music Platform thinks should be on the server, and highlights the differences. If there are differences, your email system may not function the way you expect it to.
The page has two tabs, Email Addresses and Mailing Lists, detailed below...