After I process my first account ([email protected]) - meaning most likely after I delete all newly arrived to my first account (red marker 1), I switch to my second account (red marker 2). After selecting one of the newly arrived emails, it takes a very long time to see the content of that email. I usually do not want to wait, so I select some other email in my second account - which gets displayed immediately. Now selecting the email message that would not show up, it gets displayed right away.
This seems to me as if switching from 1st account to 2nd account does not fully establish the context for the 2nd account.
PS I wrote after I delete all newly arrived to my first account because in the election year I only get junk mail
I have noticed something similar, and it doesn’t even have to be a newly arrived email or another email account. Sometimes when switching folder, the default message selected takes ages to display. Switching to another message and then immediately back to the first solves the problem. I can later select any message in that folder and it will then immediately display.
My IMAP sync settings should make the messages immediately viewable, but it does not seem to be the cause.
I concur with your findings and am adding that I do not have the same sync settings as you do, so I am more likely to suffer from this delay. Let me add that I am also a very enthusiastic eM Client user, to the point that I rushed to purchase my license despite having 20 more days of free use of the pro version.
This one of the best software products I encountered in over 40 years