The error is caused because of incorrect form validation, I analyzed the front end html code and it seems like the mail address input field data validation doesnt have the correct value. It can be fixed by changing it to the right value and I can get it done.
I have a good knowledge in html, css, javascript and php, so I am confident that I can fix this issue without affecting the existing code and its functions. I have more than 8 years of experience in web development and designing, you shall expect a professional service and good communication from me.