An email migration marked Completed can still have individual messages or labels that did not import. Verify the source, mapping, selected scope, and detailed reports before deleting the source mailbox or starting the entire migration again.
Check the configured migration scope
Confirm the source account, target account, date range, selected folders or labels, and exclusions supported by the tool you used. Google’s data import tools differ by source, so do not apply instructions for a consumer Gmail import to every Exchange or IMAP migration.
Compare representative messages across the intended period, not just the newest Inbox items. Label and folder counts may not map one-to-one to Gmail’s conversation display, so a visible count alone is not a complete completeness test.
Read the item-level and user reports
Google’s current data import tool provides import reports and, for supported sources, a user report. The user report is not available for consumer Gmail imports. Authorized super administrators can export the available reports from Data, Data import & export, Data import.
Inspect errors, warnings, discovery failures, and skipped items. Google’s definition of Completed still directs you to the report for messages or labels that did not import. Skipped can mean an item was already imported rather than lost.
Retry only after understanding the failure
Correct a demonstrated account mapping, authorization, connection, or service-access issue. Use the tool’s supported delta import or retry process where appropriate, preserving its state and reports. Do not assume an unrelated full restart has the same duplicate-handling behavior.
Do not remove security blocks merely to import a dangerous attachment. Retain the source until the agreed sample and report checks pass and the organization’s retention owner approves retirement. Record remaining failures explicitly. A successful new-mail test verifies ongoing delivery, while migration completeness requires a separate comparison of the historical data.
Browse Gmail & Google Account help
References
- Understand email import reports | Data migration | Google Workspace Help
- About the data import tool | Data migration | Google Workspace Help
Reviewed against the linked product guidance, standards, and identified vendor or public-authority guidance on October 29, 2026. Available options and screen labels can vary by account, device, region, and organization policy.