We’ve picked it up from the APS website:
The thirteenth biennial Postal History Symposium will be held on 1-2 November 2024 at the American Philatelic Center in Bellefonte, Pennsylvania. The theme for the 2024 symposium will be “The Universal Postal Union: Connecting the World by Mail,” commemorating the 150th anniversary of the Treaty of Bern.
The event is jointly-sponsored by the American Philatelic Research Library, the American Philatelic Society and the Smithsonian National Postal Museum. The 2024 symposium will also be co-sponsored by the U.S. Philatelic Classics Society, which sponsored the 2020 Virtual Symposium held in lieu of an in-person event.
The biographies of the presenters, the abstracts of their papers as well as their presentations and session videos of previous Symposia are all available on the library’s Postal History Symposium page.
Reservation details are here.