The meeting invitation does not arrive at a Gmail account.

From a booking page, a client correctly schedules a meeting. However, the invitation cannot be delivered to a Gmail email account.

Unauthenticated email from microsoftonline.com is not accepted due to domain's DMARC policy. Please contact the administrator of microsoftonline.com domain if this was a legitimate mail. To learn about the DMARC initiative, go to https://support.google.com/mail/?p=DmarcRejection d9443c01a7336-20c13971a78si65109955ad.408 - gsmtp