If you want to delete an Exchange mailbox without deleting the user, follow these steps:

  1. Log in to Exchange Online using your account credentials.
  2. In the navigation pane, click Mailboxes.
  3. In the list of mailboxes, select the mailbox you want to delete.
  4. On the Home tab, in the ribbon, click Delete Mailbox.
  5. In the confirmation dialog box, confirm that you want to delete the mailbox and click OK. ..