3.7.1:
/oc-includes/osclass/model/Alerts.php
put:
        /**
         * Unsub from an alert + deactivate + rename email to 'deleted'
         *
         * @access public
         * @since 3.1
         * @param string $id
         * @return mixed false on fail, int of num. of affected rows
         */
        function unsub($id)
        {   $this->dao->update($this->getTableName(), array('s_email' => 'deleted'), array('pk_i_id' => $id));
            $this->dao->update($this->getTableName(), array('b_active' => 0), array('pk_i_id' => $id)); 
            return $this->dao->update($this->getTableName(), array('dt_unsub_date' => date("Y-m-d H:i:s")), array('pk_i_id' => $id));
        }
instead of
        /**
         * Unsub from an alert 
         *
         * @access public
         * @since 3.1
         * @param string $id
         * @return mixed false on fail, int of num. of affected rows
         */
        function unsub($id)
        {   
            return $this->dao->update($this->getTableName(), array('dt_unsub_date' => date("Y-m-d H:i:s")), array('pk_i_id' => $id));
        }
In this way you can search for deleted and delete more than one at once.