Happens on NC 12.0.3 (on the Cloud of Nextcloud staff):
I had 4 drafts, I deleted 2 of them via the trashcan icon of the draft. The counter on the left doesn't update but stays at 4.
The counter only updates when I reload the page entirely.

I would like to take this issue as a good first bug for RGSOC'18.
Awesome! :)
The counter (folders other than draft) doesn't get updated when we delete unread messages.
The counter (folders other than draft) doesn't get updated when we delete unread messages.
Sounds like another bug. Are you able to localize and fix it?
@ChristophWurst Actually I was having some issue with the development setup. Even after enabling the debug mode, only the build.js file is being loaded in the browser.
Sounds like you're referring to https://github.com/nextcloud/mail/tree/master/js#javascript-development? I totally forgot about that documentation, it's totally outdated. We now use webpack and always minify all JavaScript sources into a single file.
FYI if you run npm run dev it will build a development bundle of js files and watch for changes to update the bundle incrementally, which is much faster than rebuilding the whole bundle after every change.
Total is not getting updated here. Correcting this should fix this issue.
https://github.com/nextcloud/mail/blob/1e8adc04f13950256d57e8c3131222ad87e77d6f/js/controller/foldercontroller.js#L199
I think unread message bug can handled by adding Radio.message.trigger('flag', message, 'unseen', false); after line 200.
This thread has been automatically locked since there has not been any recent activity after it was closed. Please open a new issue for related bugs and questions.