Fix imapsync Migration Dates in Outlook

You ran imapsync with --syncinternaldates. You checked the logs. Everything looked clean. Then you opened Outlook, and every single email in the migrated mailbox shows the same date. What happened?

Here is the thing most administrators miss: INTERNALDATE and Received headers are two completely different date mechanisms, and Outlook does not use the one imapsync protects. The --syncinternaldates flag tells imapsync to preserve the IMAP INTERNALDATE - the server-side timestamp stored alongside each message. imapsync does this correctly in most cases. But when the destination server processes the uploaded message, it adds a new Received header to the top of the email's header chain. That header carries the migration timestamp - the exact moment the message was uploaded.

Outlook's "Received" column reads from these Received headers, not from the INTERNALDATE. So even when imapsync perfectly preserved the INTERNALDATE on the server, Outlook ignores it and displays the migration date from the Received header instead. You can verify this yourself: connect to the same server with a raw IMAP client, run a FETCH command for INTERNALDATE, and you might see the correct date. But Outlook will still show the wrong one.

This disconnect between INTERNALDATE and Received headers has burned thousands of administrators over the years (check any sysadmin forum thread about imapsync date issues - the confusion is everywhere). The imapsync documentation focuses heavily on INTERNALDATE preservation, which gives administrators false confidence. The Received header problem is a separate issue entirely, and --syncinternaldates was never designed to address it.

Open Outlook after an imapsync migration and sort the Inbox by date. Every email - whether it was sent last week or in 2017 - sits on the same date. The "Received" column shows the migration timestamp for all of them. Scroll through 30,000 emails. Same date. Same date. Same date. Finding a specific email from six months ago? Good luck. Outlook's date-based search returns everything or nothing, because every message matches the same date range.

Administrators who discover the problem typically spend hours troubleshooting on the wrong side. They rebuild OST files, delete and recreate Outlook profiles, clear the local cache, even reinstall Office. None of it works because the problem is not in Outlook. It is in the email headers sitting on the mail server. Outlook is correctly displaying what the headers tell it - the headers are just wrong. The only path to resolution is correcting the Received headers and INTERNALDATE at the server level, for every affected message.

Redate.io connects directly to the mail server and runs a safe low-level message handling process with per-message verification. Each email is analyzed to detect the imapsync migration signature in the Received header chain, separating legitimate delivery headers from the ones injected during migration. The corrected message retains every original header, attachment, and flag. Redate.io processes mailboxes on any standard IMAP server - Dovecot, Courier, Cyrus, Exchange, or any other IMAP-compatible platform that was the target of the imapsync migration.