Verified workaround | Outlook 2019 and on-premises Exchange | 8 October 2026

A field-tested troubleshooting note and step-by-step workaround from Broe Computer Service (BCS). Verified in one environment; it may help with similar symptoms in other classic Outlook releases.

Symptoms and environment

Public mail folders can be added to the top-level Mail Favorites list in classic Outlook, but the shortcuts disappear after Outlook restarts or shortly after it reconnects. Regular mailbox favorites remain. The original public folders are still present under All Public Folders.

·         On-premises Exchange; the same mailbox was used on a regular PC and a Windows Remote Desktop/terminal server.

·         Terminal server: Outlook 2019 Standard Volume, build 16.0.10417.20211.

·         PC: Outlook 2019 Retail, build 16.0.20430.20140.

·         The issue followed the affected Exchange mailbox into a fresh Outlook profile under a different Windows user on the terminal server. The same mailbox worked on the PC.

·         Another mailbox on the same terminal server did not exhibit the issue.

Workaround – exact sequence

Follow these steps for the affected public folders. Fully close Outlook between phases. Remove shortcuts only; do not delete the underlying folders from All Public Folders.

1.       Close other Outlook sessions using the same Exchange mailbox to avoid concurrent changes to Favorites.

2.       Open Outlook. Under Public Folders → Favorites, remove the affected old favorite shortcuts. Verify that the original folders remain under All Public Folders.

3.       Fully exit Outlook, then reopen it.

4.       Locate each folder under All Public Folders and choose Add to Favorites. Do NOT yet choose Show in Favorites (the top Mail Favorites list).

5.       Fully exit Outlook, then reopen it. Verify the folders are listed under Public Folders → Favorites.

6.       Right-click each of these public folder favorites and choose Show in Favorites to add it to the top-level Mail Favorites list.

7.       Fully exit Outlook, then reopen it. Wait at least 2 minutes for connection/synchronization and verify that the shortcuts remain.

8.       Also verify after a complete sign-out and sign-in on the terminal server. Optionally check a second PC using the same mailbox.

Observed result

After the rebuild, the public folder shortcuts survived multiple Outlook restarts, at least five minutes of waiting, and a full sign-out/sign-in on the terminal server. Subsequent changes to favorite membership and order on the PC were reflected on the terminal server. In the normal profile, the favorites appeared roughly 30 seconds after Outlook launched.

Troubleshooting evidence

·         Outlook safe mode, a fresh navigation file, and a separate TEST profile did not initially fix the issue.

·         The issue reproduced both with and without Cached Exchange Mode, making the OST an insufficient explanation.

·         Favorites persisted offline, but had previously disappeared after reconnecting online.

·         The Autodiscover value ExcludeLastKnownGoodUrl was already set to 1; it was not the fix.

·         Recreating an old favorite without an intervening Outlook restart did not reliably fix it.

·         A newly added public folder favorite (GDPR) persisted, prompting investigation of older favorite entries.

Technical interpretation and limitations

The evidence is consistent with older or inconsistent favorite/navigation records and mailbox-backed synchronization. The precise root cause has NOT been proven. This procedure was verified only with Outlook 2019 and on-premises Exchange in this environment; Outlook 2016, 2021, and Microsoft 365 were not tested.

Favorite membership and ordering synchronized across clients. Reading Pane state did not consistently synchronize and was adjusted separately. Avoid concurrent changes from multiple Outlook clients. No public folder content was deleted, no MFCMAPI data was edited, and no Exchange server settings were changed.