email read on iPhone not marked as read on pc

Just to add some context to this, I know of 3 people on 3 separate O365 tenants having this issue. The issue appears to be server side, as both Outlook on my home computer as well as Outlook on my office computer (2 different versions of outlook) are not showing items as read after reading them on mobile. Additionally, one of my peers who is having the same issue is reading his e-mails on a Samsung Galaxy, so the issue is not related to Apple. You will notice that if you forward, reply or mark the e-mail for follow up on the mobile device, then the read status will transfer over to Outlook.

For me this issue started about two weeks ago, and for the 2 others I know about, it started about a week ago.

On some days reading on mobile will reflect in Outlook, but most days it won't.

Lastly, my inbox has 80,000 items in it, and the other 2 I've heard from have 150,000 items, and several hundred thousand items, so I'm wondering if this is only affecting super large inboxes.

Seems Microsoft is aware - EX223434

Start time: 10/1/20 - 10:40pm

Updated: 10/4/20 - 9:59pm

They say they are rolling out a fix.

Title: Users seeing messages read on mobile device not reflecting in 
Outlook desktop client

User Impact: Users may notice that email read on their mobile device 
through the native mail app isn't showing as read in Outlook.

More info: Email will not show as read as expected in the Outlook 
desktop client. Outlook on the web appears to be unaffected.

Current status: We've validated and started the deployment of the fix to
 apply the required setting to mitigate impact. Users will begin to see 
service restoration as the fix propagates throughout the affected 
environment, which we expect will be complete by the next update.

Scope of impact: Any user accessing Exchange ActiveSync (EAS) via the 
native mail app on their mobile device may be affected.

Start time: Thursday, October 1, 2020, 3:40 PM (8:40 PM UTC)

Estimated time to resolve: We expect the fix will complete propagation 
throughout the affect environment by end of day Tuesday, October 6, 
2020.

Root cause: A recent service update revealed a latent EAS setting 
misconfiguration, causing impact.

Next update by: Tuesday, October 6, 2020, 8:00 PM (10/7/2020, 1:00 AM 
UTC)

Having the same issue, running Windows 10 Pro and iOs14.0.1, and Outlook 2019 not syncing read mail back to Outlook and vis-versa. Anybody have any steps on how to resolve?