I am trying to understand why a colleague of mine who uses Microsoft Outlook doesn't "see" the invite from my Thunderbird Lightning program, and thus can't accept it into his Outlook calendar. (I receive his Outlook calendar invites fine and when I accept the invitation they populate my Lightning calendar.) Someone said it has to do with different languages/protocols (.ics?), that Mozilla and Apple are compatible but Outlook and Gmail are not? TIA for your help,