contact form always receive in spam folder

Hi
I use the last enfold version, with the enfold contact form, and with google captcha.
My client always receive contact form in the spam folder.
I tryed to change the email sender, same result
I tryed to change the admin email to a gmail one, same result (spam folder under gmail to)

Do you have any solution to be sure that emails will arrive not in spam?
Is there a best settings to achieved that?

Regards