"Your SPAM filter does not allow the email address" error with a Google Group
|Knowledge Article Number||000222032|
Since we can't guarantee that all members of a Google Group have explicitly opted in for Marketing Cloud emails, we don't allow Google Group email addresses to be added to the My Subscriber List. Anytime you try to add a Google Group address, you'll receive the error message "Your SPAM filter does not allow the email address."
This policy protects you as the sender too. If a group subscriber lodges a spam complaint, it can negatively affect deliverability rates for your account and it will automatically unsubscribe the entire group, removing all recipients in the group from future Sends.