We also got hit by this a few months back. It also got send to all of your company's contact. We had to mail all of them back and lost face. One hour in or so

We also got hit by this a few months back. It also got send to all of your company's contact. We had to mail all of them back and lost face. One hour in or so Google made it so that the emails (even those already received and opened) were blocked. It helped to mitigate the issue. Most of the outside contact that would have received the mail received it in their spam. We learned from it and have better security now.