This is a feature that could have a huge impact in wikis using the Newsletter extension, both for Wikimedia and third parties. I had been thinking of different use cases and functionality, and I was very glad to see that @ResMar requested this feature too (see Background below).
We will need to split this feature in several discussions and development chunks in order to focus on what is simpler and most needed first.
Ideally, some (all?) of these chunks could be developed in the context of Google-Code-In-2016. While some of these features might need discussion in the Wikimedia context, they are clearly useful for third party MediaWikis (and they could be completely disabled).
- Administrators want all users subscribed to a newsletter automatically, in order to have a means to send general announcements.
- Administrators want all users subscribed to a newsletter automatically as soon as they trigger a condition i.e. joining a user group or reaching a number of edits.
- Administrators want any of the above, but sending an automatic invitation instead of subscribing users directly.
Probably each of these items deserves its own subtask.
- A parameter for LocalSettings.php in order to enable this feature. Large numbers of users could be spammed/subscribed using this feature. It is reasonable to think that it will require wide consensus before anyone can use it.
- A place in the UI to define when a certain newsletter would be subject to automatic subscriptions/invitations. The own "Manage newsletter" page, with the action only visible or accessible to administrators? (see related T154144)
- A process to subscribe to a newsletter all new users as they come...
- ... complemented by an optional one-time process to subscribe all existing users to that newsletter.
- The above for new and existing users, but only applied to users meeting a certain condition:
- Membership in a user group. Selecting which user groups opt in from a checkbox list? Examples: only Translation administrators; everybody except Bots.
- Number of edits
- The above but sending an automatic invitation instead of subscribing.
- While this feature might be ok as is for new wikis with an expected small user base, performance issues should be considered for wikis with larger userbase:
- How to handle hundreds of registrations a day?
- How to handle the subscriptions / invitations for an existing user base of thousands of users?
- Users being automatically subscribed should clearly and quickly understand what have they been subscribed to, how to manage notifications, and how to unsubscribe.
- Should we think about the possibility to have users automatically unsubscribed as soon as the condition is not met anymore? Meanwhile, it would not be the end of the world if affected users would be the ones deciding to unsubscribe manually, as they can do at any time.