You must specify mailbox names in the following format:
userid is the user that owns the mailbox and mailbox is the name of the mailbox.
For hosted domains, userid is uid@domain.
For example, the following command creates the mailbox named INBOX for the user whose user ID is crowe. INBOX is the default mailbox for mail delivered to the user crowe.
mboxutil -c user/crowe/INBOX
Important: The name INBOX is reserved for each user’s default mailbox. INBOX is the only folder name that is case-insensitive. All other folder names are case-sensitive.