Per T138166#3566833 the echo notification should be added to the new Prohibit tab.
When Echo is enabled, the tab should be renamed to "Mute / Prohibit".
Ideally the Mute list should be first on the page.
* Introduce a new tab
** The new tab should appear to the right of the 'Notifications' tab (for LTR wikis)
** The tab title should be 'Muted users'
** The Notifications mute list should appear first, with the following copy
*** Section title: Notifications
*** existing label & hint text
** The email must list should display second with the following copy
*** Section title: Direct emails
*** Label: Prohibit these users from sending me direct email
*** Hint text: Add more...
* On the 'User profile' tab
** Update the copy of MediaWiki:allowemail to: Allow other users to email me directly (Manage prohibited users)
*** "Manage prohibited users" should be linked to the 'Muted users' tab
* On the 'Notifications' tab
** At the bottom a section titled 'Muted users' should exist
** This section should contain one link, linked to the 'Muted users' tab, with cop: Manage muted users