OWAでのExchange IMAP Migration移行日付の修正

Outlook on the Web (OWA) is the browser-based メールクライアント for Exchange Online and on-premises Exchange Server. After an Exchange IMAP migration, OWA displays the 移行日 for every email because it reads the same PR_MESSAGE_DELIVERY_TIME property that Outlook desktop uses. This property is set during the migration upload process and reflects the timestamp when Exchange processed the message, not when it was originally received.

OWA's date display is consistent with Outlook desktop: every email in 受信トレイ, 送信済みアイテム, and other folders shows the 移行タイムスタンプ. Unlike some web-based メールクライアントs that reference the Dateヘッダー for display (like Gmail web), OWA reads from Exchange's message store, where the delivery time is permanently set to the 移行日.

For 組織s that primarily use OWA (common in environments where IT does not deploy Outlook desktop, or for ユーザー who prefer browser-based access), the impact is identical to the Outlook desktop experience. Every email appears to have been received on the same day. Users lose the ability to browse their メールボックス chronologically, search by date, or use OWA's built-in filtering to find messages from specific time periods.

OWA displays the 移行日 in the message list for every email. The "Focused Inbox" and "Other" tabs both show messages with the wrong received date. OWA's search functionality, which supports date filters like "received:this week" or "received:last month," returns incorrect results because the indexed delivery time is the 移行タイムスタンプ.

OWA's conversation view groups messages correctly by thread (using subject and message-ID), but the date shown next to each message in the conversation is the 移行日. Users who hover over the date to see the full timestamp see the 移行日 and time. OWA's "Filter" feature, which allows quick filtering by date range, becomes unreliable. For ユーザー who work exclusively in OWA, there is no alternative view or workaround that reveals the correct 元の日付s without inspecting each email's raw headers individually.