src/Mail/mime.php
function addTo($email)
    {
        if (isset($this->_headers['To'])) {
            $this->_headers['To'] .= ", $email";
        } else {
            $this->_headers['To'] = $email;
        }
    }
function addTo($email)
    {
        if (isset($this->_headers['To'])) {
            $this->_headers['To'] .= ", $email";
        } else {
            $this->_headers['To'] = $email;
        }
    }
Add an email to the To header
(multiple calls to this method are allowed)

@param string $email The email direction to add

@return void
@access public