When I create an invite from my Outlook (both web and application) and invite people who use a Gmail address (Google Calendar), they receive an email from the invite, but they cannot accept or reject it. The email contains no information whatsoever, except for a separate .ICS file. This file cannot be opened and gives the error message: Cannot load appointment data.
The strange thing about this story is that sometimes it works, and the Gmail recipient can accept the invite (which then also becomes visible in Google Calendar). However, this seems completely random. I sent about 30 invites to the same person last week, with exactly the same content and settings on the date after. 3 invites worked as they should, the rest caused the aforementioned problems. I have tried to find out what the difference might be. But I really can't find any difference between the invites that work and the invites that don't work.
I use Microsoft 365 Business Standard through my hoster Strato.
(I also asked this question on the Tweakers.net forum. Another user indicated that he had experienced exactly the same problem for about 1 week)
In the meantime I have discovered the following. When I open the NOT working .ICS file in notepad, I see the following information at the bottom: