The documentation available when running a Discover Accounts task is available here:
https://support.quest.com/technical-documents/on-demand-migration/current/user-guide/6#TOPIC-1663903
There are two options when running a Discover Accounts task.,
Note: To collect mailbox statistics of the discovered accounts, the option is available under the Mailbox tab.
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For further details check out our product page
https://www.quest.com/products/on-demand-migration/