Client not seeing his emails

Question:
I have a client I created a site for, I added him as Co-Owner to his site so that he would be able to receive and respond to the emails coming from his website using his email address. Problem is he is still NOT receiving the emails… I don’t know what I’m doing wrong. He’s the only client having these issues.

Product:
email

What are you trying to achieve:
Way for my client to see and respond to emails from his website

What have you already tried:
Adding him as a Co-Owner on his site

Additional information:
He needs to be able to see and respond to the emails coming in from the contact form on his website

Did he check the spam/other/junk folder?