You are "Following" (subscribed to) 5 forums - getting notices of ALL activity in them.
Email notifications for that many forums is not how I would manage my participation on a Mac*
I am "interested" in at least as many (more) and have made browser bookmarks for each - I prefer the more professional "view" afforded by adding "/content + parameters" to the end of the "simple" URLs for forums
I get all of my URLs to bookmark from Site map of Communities and Categories <(read this. there are other good tips contained therein)
See the difference?
[left] https://discussions.apple.com/community/mac_os/quicktime/content?filterID=contentstatus[published]~objecttype~objecttype[thread]
> [right] https://discussions.apple.com/community/mac_os/quicktime
* In answer to your direct question about Mail.
Set up filters for what's in the titles to sort them into custom mail-inbox folders
All subject lines begin with the "forum name" in brackets followed by the thread title
Notice of this thread looks like this > [Using Apple Support Communities] - Mail Volume [c89bzy-72e45-k6tl1]
Filter by the bracketed text at the beginning, not the "code" at the end