- Gmail web IU
You can create a custom rejection notice by following these steps:
- Create a group and add the suspended users as members of the group.
- Then, go to Apps > Google Workspace > Gmail icon.
- Select Default routing and click either Configure or Add another rule.
- In the first section of the default routing rule settings please select Group membership and enter the email address of the group that you've created.
- Then, in the second section select Reject message and enter a custom rejection notice.
- In the last section select the option that says Perform this action on non-recognized and recognized addresses.
- Save the rule.