What I'd recommend is more like:

• add a sane user-to-user private messaging system that integrates with Echo, and so provides email and on-site notifications by default
• kill Special:EmailUser with fire
• redirect one to the other

But adding echo notifications onto special:emailuser is probably an ok intermediate step. :)

Prioritization and scheduling of this bug is tracked on Mingle card https://mingle.corp.wikimedia.org/projects/flow/cards/250

This was suggested by someone on enwiki too, and I agree.

Just as Mentions solves the need to use {{talkback}}, this feature would solve the need to use {{You've got mail}}.

It's feature request #7 in the list of selected bugs and feature requests (https://en.wikipedia.org/wiki/Wikipedia_talk:Notifications#Echo_-_selected_open_bugs_and_feature_requests)

This should be easy enough to implement.

• In core, the EmailUserComplete hook needs to be extended to give the User objects, and not just their emails (since emails are technically not unique)
• In Echo the new event has to be defined and hook has to be handled, the code for this should be similar to existing ones like 'welcome' or 'user-rights' events (but has to be carefully found, copied, pasted and corrected).

The new code should be smart and must not trigger an additional echo e-mail which might have been configured for other cases. Perhaps a new notification class, not necessarily with opt-out, like e-mail-has-changed which has no echo-preference entry.

Change 239582 had a related patch set uploaded (by Umherirrender):
Add a emailuser web notification

https://gerrit.wikimedia.org/r/239582

Change 239582 merged by jenkins-bot:
Add an emailuser web notification

https://gerrit.wikimedia.org/r/239582

@Umherirrender resolved, or is there still something which needs to be done?

I learnt that it was intentional.

The idea is that those who are frequently checking their mail account should not be bothered by the echo system, while others using a separate account for wiki affairs (like me) never check this mailbox until notified.

Both viewpoints are valid, but there is only one default; opt-in or opt-out approach. Personally I would tend to opt-out preference.

https://de.wikipedia.org/wiki/Benutzer:PerfektesChaos/E-Mail-Hinweis

In T56130#1684505, @Nirmos wrote:

The option is there, but it is not enabled by default. I cannot imagine that this is intentional.

Feel free to open a new task, if you want a change of this. Maybe other people also think about. I have choose this way for the reason PerfektesChaos wrote.

In T56130#1685050, @Umherirrender wrote:

In T56130#1684505, @Nirmos wrote:

The option is there, but it is not enabled by default. I cannot imagine that this is intentional.

Feel free to open a new task, if you want a change of this. Maybe other people also think about. I have choose this way for the reason PerfektesChaos wrote.

Filed as T133927: Enable by default "Email from other user" notification on all wikis