I’m personally using a regular email address, with a Google account tied to it, for my Google Calender, and I suppose that some of these things, may be because Google Workspace is doing certain things slightly different, when it has (full) access to the domain of Google Calendar invites and notifications.
But most messages that I find easily, with an envelope address on the mentioned host name “calendar-server.bounces.google.com”, they all seem to originate from:
From: Google Calendar <[email protected]>
or
From: "John Doe (Google Calendar)" <[email protected]>
Meaning that @google.com should be the recipient of the DMARC reports.
However, when dealing with free Gmail addresses (@gmail.com) though, what I see, is matching header From: and SMTP MAIL FROM, like this:
Return-Path: <[email protected]>
Sender: Google Kalender <[email protected]>
From: John Doe <[email protected]>
For my regular email address, with a Google account tied to it, I can add that I once received a DMARC report, and was having the kind of moment like “who on earth is impersonating me now, ... I didn't send anything”.
The time frame for the DMARC report was consistent to a Google Calendar invite that I sent.
And it also turned out, that it was a Google mail server, but that one did in fact “spoof” both my header From:, so I received the DMARC report, but also the SMTP MAIL FROM.
The DMARC report was from from Microsoft Outlook.
So although I would say Google Calendar is related, when seeing that exact SMTP MAIL FROM, … it still doesn’t seem like we can count on (much) consistency from Google here.
It looks like depending on the situation at hand, such as e.g. Google Workspace, free Gmail, regular email account w/Google Account, … and so on, that things may change (slightly).
