Unsubscribe button that actually unsubscribes
Currently unsubscribing from a group does not actually stop emails from being sent to your personal inbox.
The behaviour should be: If a user unsubscribes from a group, they are unsubscribed. Yes, it seems obvious, however Microsoft acknowledged the intended behaviour for unsubscribing is to still send emails to the unsubscribed user's inbox.
For more context see the forum thread.
Updating this UserVoice suggestion, last year, we announced “Follow in inbox” and other improvements with the messages you get from a group.
This includes not getting any group messages in your inbox: https://techcommunity.microsoft.com/t5/Outlook-Blog/Introducing-Follow-in-inbox-and-other-improvements-for-managing/ba-p/102611
Nerd Glow commented
I just spent a couple of afternoons with phone support for this. It's a bit misleading to have the "subscribe members" option when creating a group that doesn't seem to have any functionality. I look forward to a future roll out with a fix for this.