My company is using Google Workspace configured with one primary domain foo.com, and another domain alias foo.ai. All mail is sent and received from foo.com and foo.ai exists for backwards compatibility only.
Recently we've encountered a small number of cases where an external Gmail user never receives a Calendar invite we send them. To clarify, this is not an issue with invite responses, but with the invites themselves. Other attendees of the same Calendar event who are part of our Workspace have received the invite.
We never receive any bounce or rejection errors, and the invitees report that the invites have not been marked as spam. It's as if they were never sent.
Both domains are configured with SPF and DKIM, and DMARC is configured with none policy. I've verified the configuration with Google's MX and message header tools and everything seems in tact, and the DMARC reports are clean. I realise that the mechanism that sends Calendar invites may be different to the one that sends our mail, which may be part of the issue.
When do I begin to investigate this?
