I think it's a signature. You should log in to your email account, then click Setting - >See all settings -> Signature. In this section, you can remove the signature and make another. If this does not work, you should contact the support team directly for help. This would solve your issue more quickly.
Hope it helps!
It was my client's shop, I recommended him to contact the support team. I didn't hear him back. Maybe you have to contact with the support team.