...

                $extension = pathinfo($attachement, PATHINFO_EXTENSION);

                $basename = pathinfo($attachement, PATHINFO_BASENAME);

                if ($extension === 'ics') {

                    $mailSymfony->attachFromPath($attachement, $basename, 'text/calendar');

                    $mailSymfony->attachFromPath($attachement, $basename, 'text/calendar; METHOD=REQUEST');

                } else {

                    $mailSymfony->attachFromPath($attachement, $basename,);

                }