Fix Manual IMAP Copy Dates in Apple Mail

Apple Mail makes it dangerously easy to break your email dates. Drag messages from one IMAP account to another, drop them in the destination folder, done. Except Apple Mail does not preserve the original date metadata during this operation. When Apple Mail uploads a message to the destination IMAP server, it does not pass along the original INTERNALDATE from the source server. The destination server records the upload timestamp as the new INTERNALDATE.

And Apple Mail has no workaround for this. Unlike Thunderbird (which at least offers a column option to display the Date header), Apple Mail's message list shows exclusively the IMAP INTERNALDATE. No hidden preference, no terminal hack, no plugin can change this behavior. The date you see next to every message is the INTERNALDATE, and after a manual IMAP copy, that date is the day you performed the copy.

Most Mac users who drag emails between IMAP accounts have no idea this will happen. Apple Mail gives zero warning. You consolidate 6 years of email from an old provider into your new account, close your laptop feeling productive, and open it the next morning to find every single transferred message showing yesterday's date. If you already deleted the originals from the source account? The correct dates are gone from every client. Only the Date header buried inside each message body still holds the truth - invisible to Apple Mail's interface.

Open Apple Mail on your Mac after copying 12,000 emails from your old provider. Every message in every folder shows the same date - the day you did the copy. Your inbox, your sent folder, your project archives. All identical. Sorting by date does nothing because there is only one date. Finding that contract discussion from November 2021? Good luck scrolling through a flat, unsorted list of thousands of messages.

On iPhone and iPad, the same corrupted dates follow you. Smart Mailbox rules on macOS that filter by "Date Received" produce absurd results - either catching every copied message or none of them, depending on timing. And here is the part that catches people off guard: Spotlight search on macOS indexes Apple Mail messages using the INTERNALDATE, so even searching for emails outside of Apple Mail (using Cmd+Space) returns wrong results for date-filtered queries. The damage extends well beyond the Mail app itself.

Redate.io restores these dates through header chain analysis and date metadata reconstruction. The process reads each email's original Date header, performs per-message verification, and corrects the server-side date metadata without altering message content or attachments. Once corrected at the server level, Apple Mail on every Apple device syncs and displays the original dates automatically.