Google is now prominently highlighting a setting (as seen in their email below, promoting how it is "now easier to block spam") that affects all scheduling tools, including Mixmax.
Those considered "to be known" are senders in your contacts, company, or someone you previously interacted with.
Events set up for calendar invitations will only be added if you have had a previous interaction with your invitee. First-time invitees must confirm their booking by clicking a confirmation link in their email.
To allow calendar invitations to be added automatically to the Google Calendar, users can do either of the following:
a. Set the Calendar to add invitations "From everyone":
Click the gear icon on the top right-hand side of Google Calendar and then select Settings.
Under General, click Event settings.
Under Add invitations to my calendar, select From everyone.
For more information, check out the Google article on how to manage calendar invitations.
b. Clicking the I know the sender button when receiving the confirmation email regarding the "Invitation from an unknown sender."
If the message above didn't appear, this could be done by clicking the Know this sender? link in the confirmation email like below:
Once invitees have done either of these, they should click Yes on the event invitation to ensure it is added to their Google calendars.
Additional Recommendations
To mitigate the potential impact, Mixmax has you covered!
On the SMB, Growth, or Enterprise plans, users can set up the Mixmax meeting templates to include scheduled message follow-ups after a meeting is booked. This can also be used to prompt invitees to accept the Google Calendar invite. To learn more, see how to set up the meeting reminder emails.
