I received an email about threads and Mastadon a bit ago. The thing is I deleted my Mastadon account a hot minute after I created it. The email has no way to unsubscribe from it 
I would like to be comforted that I’m overthinking this. My Mastadon account was a couple of years ago in both creation and deletion. It’s incredibly disconcerting.
Hopefully you can get it all sorted out. I guess the account was with Eugen’s instance, mastodon.social? Sorry, I initially misread your post.
If you look at the email screenshot it’s from sdf.org. They’re pretty awesome and I’m guessing it’s just some sort of oversight. OP should just send them an email and I’m sure they’d resolve it.
Oh, absolutely! Good people.