Hi,You can do validate the email and password fields using regular expressions according to the below code:
 @api.constrains('email')
    def _check_email(self):
        for record in self:
            if record.email and not re.match(r"[^@]+@[^@]+\.[^@]+", record.email):
                raise ValueError("Invalid email format")

    @api.constrains('password')
    def _check_password(self):
        for record in self:
           if record.password and not re.match(r"^(?=.*[A-Za-z])(?=.*\d)[A-Za-z\d]{8,}$", record.password):
                raise ValueError("Invalid password format. It must contain at least 8 characters, including one letter and one digit.")

Hope it helps