Fix imapsync Migration Dates in Google Workspace

imapsync is the go-to tool for migrating mailboxes to Google Workspace. Open-source, scriptable, battle-tested across thousands of migrations. But here is the catch: Google Workspace's IMAP gateway does not behave like a standard IMAP server when it comes to date handling.

When imapsync uploads a message via the standard mail transfer protocol with the --syncinternaldates flag, it requests Google to preserve the original INTERNALDATE from the source server. Google Workspace accepts this request for some messages but silently overrides it for others. The override depends on how the message passes through Gmail's internal processing pipeline - spam filters, compliance checks, header validation. Each step can reset the INTERNALDATE to the current timestamp. There is no warning, no error log, no indication that the date was changed.

But INTERNALDATE is only half the problem. Google Workspace also adds a fresh Received header to every uploaded message, timestamped with the migration date. This Received header sits at the top of the header chain, and any IMAP client that reads the mailbox (Outlook, Apple Mail, Thunderbird) will display this migration timestamp instead of the original date. The result? A mailbox where 47,000 emails all appear to have arrived on March 15th, 2025.

What makes Google Workspace particularly deceptive is that the Gmail web interface uses the Date header for display - which imapsync does not modify. So the admin checks Gmail in the browser, sees correct dates everywhere, and assumes the migration succeeded. Meanwhile, 200 employees connecting through Outlook see a wall of identically-dated emails. Have you ever tried explaining to a CFO why every email in her mailbox now shows yesterday's date?

The Gmail-vs-IMAP split creates a two-tier reality inside the same organization. Users on the Gmail web interface see nothing wrong. Users on Outlook, Apple Mail, or any mobile IMAP client see every migrated email stamped with the migration date. When a team member references "that email from last October," colleagues see different dates depending on which client they use. Confusion turns into distrust of the entire mail system.

Then there is the compliance angle. Google Vault - the tool organizations rely on for legal holds and eDiscovery - behaves unpredictably with corrupted dates. Some Vault searches reference the Date header, others use the INTERNALDATE. A legal discovery request for "all emails between January and March 2024" might return incomplete results because the INTERNALDATE says the messages were delivered in 2025. For organizations in regulated industries (healthcare, finance, legal), this is not an inconvenience. It is a liability.

Redate.io connects to Google Workspace through domain-wide delegation and runs its proprietary correction engine across affected mailboxes. The engine performs multi-stage header analysis to identify imapsync migration signatures, then applies targeted metadata correction without altering the actual message content. Every corrected email is verified individually before the original is moved to a backup label. The admin dashboard tracks progress across all mailboxes in real time - 50 mailboxes, 500 mailboxes, it scales the same way.