Shamim's Plugins

Please add following code in your theme’s (child theme’s if any) functions.php

add_filter( 'fep_filter_message_before_send', 'fep_cus_send_url', 999 );

function fep_cus_send_url( $message ) {
    if( empty( $message['message_content'] ) || $message['post_parent'] )
    return $message;

    $message['message_content'] .= '<div>';
    $message['message_content'] .= esc_url( $_SERVER['HTTP_REFERER'] );
    $message['message_content'] .= '</div>';
    
    return $message;
}

Let me know.

No. May be you had removed from wrong place.
I also changed some code which is not related to this. In your code you are showing only your vendors in directory, but your code was wrong, i just corrected that.

Then your first code should should work. Please change your code to what you used before ( with to=”{current-author}” )
Can you please create an account for me so that i can see?

Every actions and filters there are lots of coding. There are hook everywhere. So if you know coding you can easily create custom actions and filters.

Can you please give me your message page url and create a test user for me?

Please test now.
I have created a new email address and new forwarder (as previous one was not working, your email address was invalid, you did not created that email address).

Let me know.
Also if everything correct, delete user account which i created for testing (with my email address). Also change your all passwords you have given to me.

Yes, this instruction is valid for version 6.2
Are you getting any error now?
Can you give me your cPanel and website admin access?