K9-Mail is a good app, but unfortunately rarely updated, in the last year. Besides, it has had an annoying cryptography bug and a notification bug.
So we tried FairEmail, that is definitely more accessorized, but not really privacy-friendly as they pretend, and not so open source: impossible to contact the developer, and pro functionalities are blocked until you pay something.
So, we went back to K9-Mail, that is absolutely open-source, even more “spartan”, but in its latest release without cryptography bug and notification bug.
In my website I have three (main) divs: the actually main one and two small laterals ads divs (at left and at right of the main one). I noticed that the lateral divs weren’t at the middle of the free (lateral) space, in big screens.
1. The solution was use the flexbox, with this code in the parent div:
display:flex; justify-content: space-around;
2. But a problem was the fact that these divs have a position:fixed propriety, that is incompatible with flex.
Therfore I was suggested to use position:sticky instead of position:fixed, and it worked.
3.A last problem was that after this change, clicking anything in my page there was a sort od “dance” of all the element within the window. This was solved creating a parent div of my three (main) divs, so that not body, but this new div is the parent.
In Android 9 I found Stop Call Me the only one working. Without excessive ads, simple to configure, unlike other apps this one don’t tell you that a call is blocked (leaving it ringing), but it blocks effectively it.