I found the following on HP's website. This answers my question.
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HP Surestore/StorageWorks Autoloader 1/8 - HP SureStore/StorageWorks Autoloader 1/8 has no Mail Slot from Software Perspective
ISSUE:
Despite clearly having a physical mail slot, from a software perspective, the HP Surestore Autoloader 1/8 does not have a mail slot. This occurs because every slot in the product temporarily serves as a mail slot in import and export operations. Software and SCSI specifications require a dedicated mail slot and the HP Surestore Autoloader 1/8 is handled as if it does not have a mail slot.
SOLUTION:
Because import and export operations cannot be done through software, all import and export operations must be carried out via the front panel. This means the software may not accept these operations. Therefore, if the software does not automatically re-inventory the slots after an import or export operation, the user will need to manually initiate the software in order to re-inventory the slots. If this is not done, the software will not have the correct inventory data because it will not recognize the tapes in the autoloader.
NOTE: Do not import or export cartridges from the front panel during a backup or restore operation because this may cause the operation in progress and any scheduled operations to fail.