Use the initial enquiry to describe the opportunity without sensitive attachments. Identify what evidence exists, then arrange the appropriate review and transfer method.
Inventory before transfer
A short index can identify the document owner, date and relevance without disclosing its contents. It is a preparation aid, not a substitute for evidence ultimately required by the process. Give the index five columns and keep it to one page: the document, its custodian, its date, one line on what it would show, and the clearance still required.
Sorting by the last column tells you immediately which records are available now and which depend on somebody else's decision. Send that page first and let counsel say what is needed, because a large unfiltered transfer costs review time and often contains material the case never uses. Where a record cannot be released at all, ask whether the same point can be established another way, for example by a dated statement from the person who supervised the work.
Update the index as documents are cleared or refused, and note the reason for a refusal, since that reason is frequently the fact explaining why alternative evidence was used. A file that shows its own gaps is easier to defend than one that quietly leaves them out. Store the index with the file rather than in a mailbox, so the next person can see the state of the evidence without reconstructing it.