Issue with email notifications

Hello,

The email notifications to admin are configured to go with From: addres equal to the address reported in the form. I have noticed that our mail server (hosted in another server) was rejecting these messages because they came from the address of the WP site, which does not match the domain in the From: field.

I have found a workaround: Send emails notifications From: the admin user (which should be a user of the same mail server) and add a Reply-To header with the address reported in the form. This way it worked fine. Please check.

The changes are in line 543:

//$ai_admin_headers .= "From: ".$ai_name." <".$ai_emailadmin.">\n";
        $ai_admin_headers .= "From: ".get_bloginfo("name")." Contact Form <".$ai_emailadmin.">\n";
        $ai_admin_headers .= "Reply-To: ".$ai_name." <".$ai_email.">\n";

https://wordpress.org/plugins/responsive-contact-form/