Define the collection boundary
Record custodians, account identifiers, folders or locations, dates, queries, permissions and export options. Save completion reports, error records and details of retries. Explain whether the output contains search hits, additional partially indexed material or separately collected linked content. A download completing successfully does not establish that every relevant source was included.
Check what can fall outside
Separate mailbox content from audit logs, message tracing, archives, backups and endpoint artefacts. Encryption, unsupported content, indexing limitations and query interpretation can affect results. Some collection systems distinguish a successful operation from a partially successful one. Preserve the status information rather than reporting only the final number of files.
Report a bounded result
A proportionate collection can still be appropriate. The report should make its boundaries clear and explain why they answer the agreed question. Maintain original export packages and derived examination files separately, with recorded hashes for each. If the matter expands, the collection record should show whether further work is possible. A claim such as all email was imaged is unsuitable unless the actual method, sources and completeness evidence support that description.
Sources & further reading
Primary references support the technical explanation. They do not establish D3 validation of a particular method.