@IvoA1975 Is "Attachment download behavior" set to "Manual" in "Configuration > Synchronization"? If so, changing it to "Auto" might help.
The TestFlight release also has a few changes that might help with this. Specifically, it improves the display of HTML notes (emails are saved as HTML notes). The TestFlight release should be made stable and released to the AppStore some time in the next few weeks.