YouTube connected to mac email?

I'm sorry if this has been posted before, I'm new here and did a search for this issue but didn't bring up anything.

When someone emails me, my YouTube account name and thumbnail (which I don't even use anymore) show up as part of my mac.com alias. I thought I disconnected everything to do with YouTube that I could from my mac.com account, and I'm not even sure how they got linked in the first place. I can't understand at all why it's linked. I use it for a lot of formal emails and it just looks ridiculous.

If anyone has any ideas, I'd really appreciate it. It's probably something really simple that I have somehow missed and will feel really silly!

 

Any ideas?