Fix GSMMO Migration Dates in Apple Mail

Here is the frustrating part about GSMMO migrations: Google's own migration tool corrupts your email dates, and Apple Mail has zero ability to work around it. When GSMMO uploads emails from Outlook PST files or Exchange profiles into Google Workspace, it stamps each message with the upload timestamp as the INTERNALDATE. The original Date header stays intact inside the message body, but the server-level date metadata gets overwritten with the migration date.

Why does Apple Mail care about this? Because Apple Mail on macOS and iOS reads exclusively from the IMAP INTERNALDATE to determine the date shown next to each message. Unlike the Gmail web interface (which reads the Date header and may display correct dates), Apple Mail never parses the Date header for its list view. There is no setting to change this. No hidden preference. No terminal command. Apple Mail shows the INTERNALDATE, period.

The result is brutal for anyone who migrated to Google Workspace using GSMMO and then opened Apple Mail. Inbox, sent items, drafts, archived folders - every single message displays the date GSMMO ran. A 2019 migration means 15,000+ emails all showing the same April 2019 date. Smart Mailboxes that filter by date become useless. Chronological threading disappears entirely from the message list. And Mac users who rely on Spotlight to search emails by date range? Those results are wrong too, because Spotlight indexes the INTERNALDATE from Apple Mail's cache.

Picture this: you open Apple Mail on your MacBook, and your entire inbox shows "April 11, 2019" next to every message. Emails from 2015, emails from last week, client proposals, invoices, personal threads - all stamped with the same date. The "Date Received" column in Apple Mail's column view is identical for thousands of messages. Sorting by date? Pointless. Every message clusters under one day.

On iPhone and iPad, the same problem follows you. The Mail app pulls from the same corrupted INTERNALDATE. Smart Mailbox rules on macOS that use "Date Received is in the last 30 days" either catch everything (if GSMMO ran recently) or nothing at all. And here is something most people miss: Spotlight search on macOS indexes Apple Mail messages using the INTERNALDATE, so even searching for "emails from December 2022" outside of Apple Mail returns garbage results. The corruption ripples through the entire Apple ecosystem.

Redate.io addresses this through a proprietary correction engine that performs targeted metadata correction without altering message content. Each email is individually verified before and after processing. Once Redate.io corrects the server-side date metadata, Apple Mail on every Apple device syncs automatically and displays the original dates.