Outlook Cached Exchange Mode Shows Old Mailbox Name: Fix

After a user is renamed in Microsoft 365 or their display name is changed in Exchange Online, Outlook in Cached Exchange Mode may continue to show the old mailbox name in the folder pane. This happens even after restarting Outlook or waiting for the offline address book to update. The root cause is a locally cached profile property that Outlook does not refresh automatically. This article explains why the old name persists and provides a reliable fix that forces Outlook to sync the updated display name.

Why Outlook Still Shows the Old Mailbox Name

When a user’s display name is changed in Exchange Online, the Microsoft 365 admin center or Exchange admin center updates the attribute on the server side. Outlook in Cached Exchange Mode stores a local copy of the mailbox data, including the display name, in an offline data file with an OST extension. This local copy is not automatically refreshed when the server-side name changes.

The Outlook Address Book service, which handles name resolution and folder pane labels, reads from the local cache first. Because the cached name in the OST file still points to the old display name, Outlook continues to show it in the folder pane and in the address book. Simply restarting Outlook or sending and receiving does not trigger a full refresh of this cached property. The fix requires temporarily disabling Cached Exchange Mode so Outlook pulls the name directly from the server and overwrites the old cache.

What Does Not Fix the Problem

Clicking Send/Receive All Folders, rebuilding the Outlook Address Book, or running the Offline Address Book download tool does not resolve this specific name display issue. The cached mailbox name is part of the OST file metadata and is not updated by those actions. Deleting and re-creating the Outlook profile also works, but that method is more disruptive because it removes all cached data and requires reconfiguring email accounts.

Steps to Force Outlook to Show the New Mailbox Name

The following steps work for Outlook 2016, Outlook 2019, Outlook 2021, and Microsoft 365 Outlook on Windows 10 and Windows 11. The procedure temporarily turns off Cached Exchange Mode, restarts Outlook, and then turns it back on.

1. Open Outlook and go to Account Settings
   Click File in the top-left corner. In the Info section, click Account Settings and then Account Settings again from the dropdown menu.
2. Select the Exchange account and click Change
   In the Account Settings dialog, select the Microsoft Exchange account that shows the old name. Click the Change button above the list.
3. Open More Settings
   In the Change Account dialog, click More Settings in the bottom-right corner.
4. Switch to the Advanced tab and uncheck Cached Exchange Mode
   In the More Settings dialog, click the Advanced tab. Under the Cached Exchange Mode section, uncheck Use Cached Exchange Mode. Click OK to close the dialog.
5. Click Next and then Finish
   Back in the Change Account dialog, click Next. Wait for Outlook to test the connection. Click Finish to close the dialog.
6. Restart Outlook
   Close Outlook completely. Wait 10 seconds and then reopen Outlook. When Outlook starts, it will connect directly to the Exchange server in Online Mode. The folder pane should now show the new mailbox name.
7. Re-enable Cached Exchange Mode
   Repeat steps 1 through 4. This time, check Use Cached Exchange Mode in the Advanced tab. Click OK, then Next, then Finish. Restart Outlook one more time.

After the final restart, Outlook will download a fresh offline cache. The folder pane and address book will display the updated mailbox name. The entire process takes about five minutes.

If Outlook Still Shows the Old Name After the Main Fix

Outlook displays the old name in the address book but not in the folder pane

This indicates the Offline Address Book has not downloaded the latest display name. In Outlook, click Send/Receive and then Send/Receive Groups. Select Download Address Book. In the dialog, check Download changes since last Send/Receive and click OK. Wait for the download to finish and restart Outlook.

The old name reappears after a few hours

This happens when the server-side name change was not fully replicated across all Exchange Online domain controllers. Wait 30 minutes and repeat the main fix steps. If the problem persists, contact your Microsoft 365 administrator to confirm the name change was applied to all user attributes, including displayName, givenName, and proxyAddresses.

Other users still see the old name when sending email

This is a separate issue caused by the recipient’s local Outlook cache or address book. The fix described in this article only affects the Outlook client where the change is made. Other users must either wait for their Offline Address Book to update or manually remove the old name from their Auto-Complete cache by deleting the entry in the To field and typing the name again.

Cached Exchange Mode vs Online Mode: Name Update Behavior

Item	Cached Exchange Mode	Online Mode
How Outlook stores mailbox name	In a local OST file	Pulled from the server each session
Does the name update automatically after server change?	No, requires manual refresh	Yes, updates after a restart
Offline access	Full access to cached data	No offline access
Performance over slow connections	Better, because data is local	Slower, because data is remote
Time to apply a display name change	5 minutes with the fix above	Immediately after restart

After completing the steps in this article, your Outlook folder pane and address book will display the correct mailbox name. To prevent this issue in the future, consider switching to Online Mode briefly after any user rename in your organization. The toggle method shown here is faster than deleting and re-creating the Outlook profile and preserves your cached email, calendar, and contacts.