Using Your Regular Google Calendar with a Different, Non-Google Email Address

When you receive a Google Calendar invite using an email address that is not associated with your Google account you will not be able to respond (accept/reject/maybe) the invitation.

Here's a workaround:

Create a Google account for whatever other email address(es) where you want to be able to receive calendar invites (for ease of reference, let's call this you@xyz.com). You will then want to make that calendar totally shareable with your normal Google Calendar account. You'll also need to stay logged into the Google account associated with you@xyz.com and then you'll be able to respond the the calendar invite. Google allows you to be logged into more than one Google Calendar account at a time. As long as you have turned on the ability to see the you@xyz.com event in your normal Google Calendar account you will be able to view the event.

Note that unless you copy it to your normal Google Calendar account the event will actually be located only in your you@xyz.com Google Calendar. Consider this when creating reminders.