Insert Current URL into MailTo link in wordpress

You are overkilling the idea of the query to get the url.

The simplest way and best way at the same time is:

<?php

    // get_the_ID() will return the current's post id
    // get_the_permalink() will return the current url
    $current_url = get_the_permalink(get_the_ID());

?>

That function will not echo, but rather return/get the permalink url for you. You can then incorporate the url by adding

...stuffbeforeurl<?php echo $current_url; ?>...stuffafterurl

into your link.