With Domino 12 a customer of mine has a similar problem to the one that is described in this support article:
Whenever the users send mails to any O365 recipient one of two things happen: If the checkbox "Some invitees use other mail programs" is not checked, then the invitation shows in Outlook as "normal mail": It cannot be accepted nor declined and does not look like an invitation at all, but it contains an ics file attachment that can be opened:
This happens although the INI-parameter from the link is set and server have been restarted.
Domino Version is 12.02 (no FP1 yet).
Now the strange thing: I have a rule that forwards my mails from an O365 test account to Domino. These forwarded invitations all look identical in Domino and work without a problem. Only Outlook cannot handle these.
First off, that iCalendar in Test 2 was generated by a Notes 9.01 client and not a 12.02 Domino server. You can tell by the PRODID value ("9.0.1//EN_C"). That means the INI you set is not likely to have any effect since Domino is not generating the MIME message, Notes is (at least for Test 2)
The odd formatting of the iCalendar in Test 2 is a minor concern since each iCalendar property should start on a new line, not be appended to other properties. I suspect that is likely just a rendering artifact since I do not recall ever hearing a customer report about bad iCalendar like that in 9.x.
The .ics attachment in Test 1 is an ancient legacy artifact from the transition period where iCalendar support was not yet implemented by some vendors (~ Domino 6.0). We attached a copy of the iCalendar portion of the message so that recipients on systems that did not grok the RFC 2447 messages could open it with a client that did understand iCalendar.
Looking at Test 1, it looks like O365 is rendering the text/html body part with the rich rendering of the workflow message. From the available info I cannot who generated the MIME message (Notes or Domino) or why O365 would only render the text/html body part and not the iCalendar. If the issue were with the iCalendar itself you would see an attachment like this:
or you may see it in the body instead of the HTMLized version of the Notes invite.
If the PRODID in Test 1 has "12.0.2//EN_S) then the message was generated by the Domino server. The INI ICAL_SendAsMultipartRelated=0 on the server may help. If Test 1 is not from the Domino server or the INI did not help then please open a case with support so that we can give you the dedicated help needed to get to the root of the problem.
You are right: The calendar entry had been generated by a version 9.0.1 Client with 9.0.1 template. We recently updated the servers to Domino 12.0.1 but not yet the clients (customer is about to migrate away from Domino and does not want to update clients.
But since the Domino update some recipients in some domains do not receive the invitations correctly anymore that definitively were ok when the servers were Domino 9 and 10.
The only thing that changed was the version of the Domino servers, hence the question.
And you analyzed the problem correctly: It is O365 that does not render the invites correctly... but that does not help when it did render them correctly with earlier Domino version...
If Domino were doing the conversions then the INI ICAL_SendAsMultipartRelated=0 should help deal with O365 rendering issues.
O365 has some very particular MIME structure requirements when it comes to iCalendar and it does not seem to always apply them (or applies them a little inconsistently). I've seen the same test message simply not appear, mis-render and render correctly.
In any case, if you want to dive more on this it would be best to open a ticket, especially if the INI does not help.
