We've upgraded discuss.grapheneos.org to use an in-memory database (valkey) for caches and sessions instead of disk storage along with using it as a queue for running more jobs in the background. The background job queue greatly improves performance for posting in threads where people are subscribed to notifications since submitting the emails to mail.grapheneos.org is now handled by a background worker. Sending emails is also now more robust because we've configured it to retry if submitting emails to mail.grapheneos.org fails for any reason. You can see the changes here:
https://github.com/GrapheneOS/discuss.grapheneos.org/compare/a53ae3b14ac5435530f07c3a6c95f8239eecdf6f...71365875383608c0f0a7b636d85965d0ef227bf7
Since sending emails is now being handled in a much better way, we can consider adding the Follow Tags extension to allow users to receive notifications when new threads are posted with a tag:
https://discuss.flarum.org/d/20525-friendsofflarum-follow-tags
Among other things, this would allow receiving notifications including optionally an email when official posts are made with the Announcements tag.