Microsoft 365でのimapsync移行日付の修正
imapsyncの移行がMicrosoft 365で間違った日付を表示する理由
imapsync migrations to Microsoft 365 (Exchange Online) face a double challenge with date preservation. First, Exchange Online's IMAP gateway has specific behaviors that can override the INTERNALDATE provided by imapsync's --syncinternaldates flag. Second, Exchange Online adds its own Receivedヘッダー during the IMAP APPEND process, stamping every message with the 移行タイムスタンプ.
Microsoft 365's IMAP implementation is limited compared to full Exchange protocols (EWS, MAPI). When imapsync uploads via IMAP, the message passes through Exchange Online's transport pipeline, which processes it similarly to a new incoming message. This pipeline adds transport headers, runs コンプライアンス checks, and stamps the message with delivery metadata that reflects the actual upload time rather than the requested INTERNALDATE.
Administrators who choose imapsync for Microsoft 365 migrations (often because it is free and scriptable) discover after the migration that date preservation did not work as expected. The --syncinternaldates flag, which works correctly with many standard IMAP servers, does not produce the expected results with Exchange Online's particular IMAP implementation. The entire migrated メールボックス shows the 移行日 across all Microsoft 365 clients.
Microsoft 365への影響
In Microsoft 365, the 移行日 appears uniformly across Outlook desktop, OWA, Outlook mobile, and Microsoft Search. Unlike Gmail (where the web client may mask the issue), Microsoft 365 clients all reference the same delivery timestamp. Users have no workaround and no client that shows the 正しい日付 until the underlying Receivedヘッダーs and INTERNALDATE are corrected at the サーバーレベル.
Microsoft 365 administrative and コンプライアンス features are equally affected. Exchange Online Protection, Data Loss Prevention policies, and Microsoft Purview コンプライアンス searches all index the 移行タイムスタンプ. For 組織s subject to data 保持 regulations, the corrupted dates mean that 保持 policies based on message age operate on incorrect data, potentially leading to premature deletion of messages that should be retained or indefinite 保持 of messages that should have been purged.
よくある質問
Why does imapsync --syncinternaldates fail with Microsoft 365?
Exchange Online IMAP implementation processes uploaded messages through its transport pipeline, which can override the requested INTERNALDATE. Additionally, Exchange Online adds Receivedヘッダーs that carry the upload timestamp. These server-side behaviors are outside imapsync control.
Should I have used a different migration tool for Microsoft 365?
Most migration tools (including commercial ones like BitTitan and CloudM) produce the same date issue because the root cause is in how Exchange Online processes uploaded messages. The migration tool choice does not prevent the problem. Redate.io fixes it に関係なく which tool was used.
Can Redate.io fix imapsync-migrated メールボックス in bulk?
はい。 Redate.io supports bulk メールボックス processing for Microsoft 365. Administrators can scan and fix multiple メールボックス from a single dashboard. The Enterpriseプラン supports up to 100,000 emails per メールボックス.