Reserved group names
We reserve certain names that cannot be used if you are creating a group using Google Groups or Google Groups for Business. However, you can use these names if you are creating a group using the Groups control in the Admin console.
The group addresses abuse and postmaster are handled differently than other reserved names. When creating these groups in the Google Admin console, you might see "Settings weren't saved because an error occurred," but the group will still be created. This error appears because the settings for the abuse and postmaster groups can't be changed. You can, however, subscribe to these group addresses and receive all mail sent to them.
Learn more about abuse and postmaster