1. DNS/google/MX
について、ここに記述してください。
Set up MX records for Google Workspace email
https://support.google.com/a/topic/1611273
11. Typically, you can send and receive messages at your new Google Workspace email address in less than 6 hours. However, it may take 48–72 hours before you receive email at your new address. It’s no fun to wait, but the time for MX records to take effect depends on your domain host. We have no control over this. In the meantime, you can get your email messages at your old email client.
Googleの言う domain host とは zone serverを指す。