Apple iOS Mail App Issue - This message has not been downloaded from the server.

I have a Microsoft Outlook.com email account that works perfectly in Outlook Web and in the Outlook iOS app. Since updating both my iPhone and iPad to iOS/iPadOS 18.6, Apple Mail shows the error “This message has not been downloaded from the server” on certain, but not all, emails. This happens on both devices and persists after:

– Completely removing the account and re-adding it.

– Deleting and reinstalling the Mail app on both my iPad and iPhone

– Clearing all mobile device registrations from my Microsoft account.

– Confirming “Mail Days to Sync” is set to “No Limit” and Push is enabled.

The affected messages open normally in Outlook Web, proving the content is on the server, but Apple Mail refuses to fetch it. This issue began immediately after the 18.6 update and appears to be a Mail app bug with Outlook.com/Exchange ActiveSync accounts. Any relevant advice gratefully received.