ACP options for account activation are confusing when emails are turned off board-wide

When emails are turned off board-wide, there are two options in account activation: "Disabled" and "None". What is the difference between disabled and none? And where are the other options?

Suggested fix:

1. Replace "Disabled" with "Registration disabled" and "None" with "Automatic activation". Some other options I though about were "Immediate activation" and "No activation", the latter one suffering from the same disabled/none confusion.

2. Add a note that the other options are not shown because emails are disabled board-wide, along with a pointer where to enable email (communication -> email).

3. Perhaps only display the note when emails are disabled.