function DoNav(theUrl)
  {
  document.location.href = theUrl;
  }

<tr onclick="DoNav('myphpscript.php');">

onclick="document.forms[0].submit();"

$(function() {
    $('tr').click(function() {
        var mail_id = /* get the mail id of this row... not sure where since I dont' have the HTML */
        $('body').append('<form method="post" action="myphpscript.php" id="donavform" style="display:none;"></form>');
        $('#donavform').append('<input type="hidden" name="mid" value="'+mail_id+'" />');
        $('#donavform').submit();
    });
});

<!-- 8435 is the mail ID in this example. -->
<tr id="row3">8435</tr>

var mail_id = $(this).html();

$('#donavform').append('<input type="hidden" name="mid" value="'+mail_id+'" />');