Google Calendar Invites Replacing Outlook Email with Gmail Address

We’re experiencing a rather weird issue where a Google Calendar Invitation meant for a Outlook email address is being sent to a Gmail address instead. We originally thought that this could be a forwarding rule setup in Outlook but there are no rules setup. Furthermore the Google Calendar invite isn’t showing up in an email trace meaning that it’s not even hitting the Outlook servers. The email appears to be kept in the Google ecosystem and as if Google is replacing the Outlook email with a Gmail address. Is there some kind of setting within Google/Gmail that would cause this type of behavior?