Fix imapsync Migration Dates in Google Workspace

imapsync is a popular choice for migrating mailboxes to Google Workspace because it is open-source, scriptable, and supports the IMAP protocol that Google Workspace exposes. However, Google Workspace's IMAP implementation has specific behaviors that interfere with date preservation. When imapsync uploads messages via IMAP APPEND, Google's mail infrastructure processes each message through its own pipeline, adding a Received header and potentially overriding the INTERNALDATE.

The --syncinternaldates flag in imapsync instructs the tool to request the original INTERNALDATE from the source server and pass it to the destination server during APPEND. Google Workspace may accept this date for some messages but override it for others, depending on the message content and how it passes through Gmail's filters. The result is an unpredictable mix of messages with correct and incorrect dates within the same migrated mailbox.

Google Workspace administrators often discover the problem when users report that their Outlook or Apple Mail clients (connected via IMAP to their Google Workspace account) show incorrect dates. The Gmail web interface typically shows correct dates (using the Date header), which adds to the confusion. A Google Workspace mailbox can appear perfectly normal in the browser while being completely date-corrupted from the perspective of any IMAP client.

The split between Gmail web (showing correct Date header dates) and IMAP clients (showing corrupted INTERNALDATE) is the defining characteristic of this issue in Google Workspace. Organizations where some users prefer the Gmail web interface and others use Outlook or Apple Mail experience inconsistent date displays from the same mailbox. Collaborative workflows break down when colleagues reference email dates that appear differently in their respective clients.

Google Workspace admin tools provide limited visibility into the INTERNALDATE issue. The Google Admin Console does not expose INTERNALDATE metadata for individual messages. Google Vault, used for compliance and eDiscovery, may reference either the Date header or the INTERNALDATE depending on the search method, producing inconsistent results in legal discovery scenarios. The only way to comprehensively resolve the issue is to correct the INTERNALDATE and Received headers at the message level.