Error in user registration

hi ,I installed xenforo and in the user log after I entered the default data I get a message saying that some fields contain inaccurate data.
Thank you

I registered on his website with gmail, i did not found any problem in registration, login log out etc.

He is using his own domain mail or some other mail

When he click on register, msg comes some fields data is inaccurate (might be registration with only specific mail domain is allowed and all other mails are not accepted)

He is using xF 1.xx with custome theme
I tried with many email services (hotmail, email, icloud, alice) after several attempts I noticed that the message appears after the mail account has been used.