There are lots of feature issues to do with trying to limit the amount of emails redmine send out and I think its fair to say the current default config is email heavy. Also not all the tools/settings are quite developed enough to allow everyone to configure emails the way they want - hence all the feature requests. I would suggest lots of people would like email notification to be a bit more granuala and transparent from the UI

Related email issues #6390 #6229 #5862 (and there are no doubt more...)

I suggest that the issue creation and update forms always list exactly which users and or roles will be notified by email so that its obvious who is getting an email.

Then as a further refinement allow users to untick some recipients from this list of email recipients. (its already possible to add new people via watchers I believe). This would mean that users can put loads of info/updates to an issue without worrying about spamming everyone and I suggest the number of unnecessary emails sent by redmine would be dramatically reduced

It would also make sense that this option can be disabled/enabled by admin/roles so the current email behaviour of notifications could be maintained if desired.

I think this would dramatically reduce unnecessary emails sent (if used sensibly!), and reduce the need for most other feature requests dealing with controlling email notifications.