Fix Exchange IMAP Migration Dates in OWA
Why Exchange IMAP Migrations Show the Wrong Date in OWA
Outlook on the Web (OWA) is the browser-based email client for Exchange Online and on-premises Exchange Server. After an Exchange IMAP migration, OWA displays the migration date 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 the inbox, sent items, and other folders shows the migration timestamp. Unlike some web-based email clients that reference the Date header for display (like Gmail web), OWA reads from Exchange's message store, where the delivery time is permanently set to the migration date.
For organizations that primarily use OWA (common in environments where IT does not deploy Outlook desktop, or for users 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 mailbox chronologically, search by date, or use OWA's built-in filtering to find messages from specific time periods.
How This Affects OWA
OWA displays the migration date 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 migration timestamp.
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 migration date. Users who hover over the date to see the full timestamp see the migration date and time. OWA's "Filter" feature, which allows quick filtering by date range, becomes unreliable. For users who work exclusively in OWA, there is no alternative view or workaround that reveals the correct original dates without inspecting each email's raw headers individually.
Frequently Asked Questions
Is the date issue in OWA the same as in Outlook desktop?
Yes. Both OWA and Outlook desktop read the same delivery time property from Exchange. The date corruption caused by Exchange IMAP Migration affects both clients identically. Fixing the dates on the server corrects the display in both OWA and Outlook desktop simultaneously.
Can I see the original date in OWA by viewing message headers?
Yes. In OWA, you can view the original Date header by opening a message, clicking the three-dot menu, and selecting "View message source." The original Date header shows the correct date. However, this is a manual process impractical for thousands of emails.
Does Redate.io fix dates for both OWA and Outlook at the same time?
Yes. Redate.io corrects the email at the Exchange server level. Once the Received headers and delivery time are fixed, the correct date appears in OWA, Outlook desktop, Outlook mobile, and any other client connected to the mailbox.