...

src/UnicaenMail/Service/Mail/MailService.php

@@ -228,7 +228,7 @@ EOS;
                 $extension = pathinfo($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,);
                 }