The 'Transaction recipient authorisation limit' field on Manage Company allows Administrators to specify a threshold at which a number of recipients will require admin approval.
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If left blank, this check will not be made.

If for example, this value is set to 10, then any transaction with 10 or more recipients will require an admin to review the transaction and approve it, before it will be delivered.

Go to Settings => Manage Company

Find the 'Transaction recipient authorisation limit' field and set the value you wish to enforce the approval requirement.