Fiery Keeper of the Hat
An electronic signature of the copyright owner, or a person authorized to act on behalf of the owner, of an exclusive copyright that has allegedly been infringed.
I'm fairly sure they just want the email to come from an account registered to the copyright holder. But esignature can mean a few different things, so I would poke around the website a bit. It's okay to email them and ask if you're really not sure.