OutlookでのExchange IMAP Migration移行日付の修正

Microsoft Exchange Server includes a built-in IMAP migration feature (available through the Exchange Admin Center and PowerShell) that allows 管理者 to migrate メールボックス from third-party IMAP servers into Exchange Online or on-premises Exchange. This native migration tool connects to the source IMAP server, downloads each message, and uploads it to the destination Exchange メールボックス.

During the upload phase, Exchange's transport pipeline processes each message as though it were a newly received email. The pipeline adds transport headers, including a Receivedヘッダー with the current processing timestamp. Exchange also sets the PR_MESSAGE_DELIVERY_TIME (the property Outlook reads for its "Received" column) to the upload timestamp. The original IMAP INTERNALDATE from ソースサーバー is not carried over to the destination Exchange メールボックス.

Administrators who use Exchange's native IMAP migration expect Microsoft's own tool to handle date preservation correctly. The discovery that all migrated emails now display the 移行日 in Outlook is unexpected, 特に because Exchange's migration documentation does not prominently warn about this behavior. The issue affects every メールボックス processed by the migration batch, and Exchange provides no built-in mechanism to correct the dates after migration.

Outlook connected to the migrated Exchange メールボックス displays the 移行日 in the "Received" column for every email. The "Sent" column for 送信済みアイテム also reflects the 移行タイムスタンプ because Exchange's transport pipeline processes 送信済みアイテム the same way during upload. The Outlook calendar pane, which references email dates for meeting-related messages, shows in正しい日付s for migrated meeting invitations and responses.

Exchange's native search (used by Outlook's search bar) indexes the corrupted delivery time. Date-based searches return wrong results. Outlook's AutoArchive feature, which moves or deletes emails based on age, miscalculates message age because it uses the 移行日. Rules that trigger on received date and Conditional Formatting rules that highlight emails by age also operate on the 間違った日付s, producing unexpected behavior across the Outlook experience.