Is there any way to see which people have "unsubscribed" from receiving emails through Realm?

In the community menu, click on communications. The last option on the left should be history. Click on it, and then you’ll see the history of communications you’ve sent out through the Community menu. For those inbox emails you sent out, you should see the option to click on more details.   That’s where you can find the option to click on the emails that were unsubscribed or undelivered.   Emails sent out through the group section under admin are not logged in this history.