Outlookでのimapsync移行日付の修正
imapsyncの移行がOutlookで間違った日付を表示する理由
imapsync is an open-source command-line tool popular among system 管理者 for server-to-server IMAP メールボックス synchronization. imapsync includes a --syncinternaldates flag designed to preserve the original INTERNALDATE 移行中. ただし、 even when this flag is used, 宛先メールサーバー adds its own Receivedヘッダー to each uploaded message, and this header carries the 移行タイムスタンプ.
Outlook does not rely solely on INTERNALDATE for date display. Outlook's "Received" column is derived from the topmost Receivedヘッダー in the email. Even if imapsync successfully preserved the INTERNALDATE using --syncinternaldates, the new Receivedヘッダー added by 宛先サーバー overrides the date that Outlook displays. Administrators who believed they had protected the dates by using the correct imapsync flags discover that Outlook still shows the 間違った日付.
This behavior catches many experienced 管理者 by surprise. The imapsync documentation focuses on INTERNALDATE preservation, leading 管理者 to assume that --syncinternaldates is sufficient. In practice, the Receivedヘッダー issue is a separate problem that --syncinternaldates does not address, because the Receivedヘッダー is added by 宛先サーバー after imapsync completes its upload, outside of imapsync's control.
Outlookへの影響
After an imapsync migration, Outlook displays the 移行日 in the "Received" column for every email. Even when --syncinternaldates was used and the IMAP INTERNALDATE is technically correct on the server, Outlook parses the Receivedヘッダーs and displays the topmost one, which is the 移行タイムスタンプ. The result is a メールボックス where every email appears to have arrived on the same day.
The frustration is compounded because 管理者 can verify on the IMAP server that the INTERNALDATE is correct, yet Outlook still shows the 間違った日付. This leads to hours of troubleshooting on the Outlook side (reinstalling profiles, clearing caches, rebuilding OST files) that never resolve the issue because the root cause is in the email headers, not in Outlook's local configuration. The only fix is to remove the migration Receivedヘッダー from each email at the サーバーレベル.
よくある質問
I used imapsync --syncinternaldates but Outlook still shows the 間違った日付. Why?
The --syncinternaldates flag preserves the IMAP INTERNALDATE on the server, but it cannot prevent 宛先サーバー from adding a new Receivedヘッダー. Outlook reads the topmost Receivedヘッダー for its date display, which contains the 移行タイムスタンプ. The INTERNALDATE and the Receivedヘッダー are two separate date sources.
Can I fix imapsync dates by editing the Receivedヘッダーs manually?
Technically, you would need to download each email, edit the headers, delete the original, and re-upload with the correct INTERNALDATE. For anything more than a handful of emails, this is impractical. Redate.io automates this entire process with built-in verification.
Does Redate.io work with any IMAP server used with imapsync?
はい。 Redate.io supports any standard IMAP server. Whether the destination was Dovecot, Courier, Exchange, or any other IMAP-compatible server, Redate.io can connect and fix the dates.