This is, I think, a not-too-serious bug report for Pegasus Mail 4.81.1154, Jan 10 2023, build ID 1154. I have received an unexciting email message containing the nasty-looking header
Subject: =?utf-8?B?8J+QpyBJdCdzIHR1cm5pbmcgY29sZGVyIC0gQmUgcHJlcGFyZWQg?=
=?utf-8?B?Zm9yIHRoZSDinYTvuI8gY29sZGVyIG1vbnRocyBhaGVhZCDinYTvuI8=?=
In the folder view top-right list of messages, the Subject column shows as completely blank. (I think it should show some text!)
In the folder view's bottom-right message preview pane, the subject appears, presumably correctly, as
It's turning colder - Be prepared for the ❄️ colder months ahead ❄️
Then when I open the message, its window title bar shows
<Sender>, ????????????????????????
That's almost as bad as completely blank, but at least I can tell there ought to be something there. The header section of the message itself shows the subject properly -- that's what I copied and pasted from to get the text earlier in this post.
The sender (trying to sell central heating radiators) has not made this subject text easy to display, but I firmly suggest Pegasus Mail ought to be able to do an equally good job in the window title bar and the message list as it does for the message window headers area.
This last bit isn't part of the bug report, but I'd guess it was an issue with character encoding.