When I get an email through EmailUser, it goes through without an echo notification and I actually get the email. When I get an email though echo (I have no idea how), I get a notification and can read the first sentence of the email, but cannot access it or read the full thing. See this picture for an example. The problem isn't with my email settings, since some that do not trigger the notification still get through.
There is no difference between "getting an email through EmailUser" and "getting an email through Echo". The notification you're seeing is because someone sent you an email through EmailUser. It's very strange that you're not receiving that email though, and you're not the first person with this problem :(