We were able to confirm Exchange is loading correct certificates, all customer branded SSL certificates are now loaded correctly.
P.S. This is why we went away from custom client-branded SSL certificates, the little bit of extra vanity isn't worth the potential performance problems.
Update 09/16/2024 14:38 PM 29 days
Mobile devices are currently receiving SSL errors such as "cannot verify server identity" or "certificate not trusted" due to the wrong certificate being loaded.
We are working on the issue and expect to have it resolved shortly. In the meantime, you can still access email on your mobile devices by opening Safari or Chrome on your phone and going to https://owa.xd.email/owa/