If I click on an ASCII-email, which is larger than 1.2 MiB to read it, it will not be shown. There is neither a warning nor an interaction with the user that this email can't be displayed.
It was in prior versions of kmail no problem to show large ASCII-emails.
STEPS TO REPRODUCE
1. Launch kmail
2. Try to read an ASCII-email larger than 1.2 MiB
Kmail doesn't give the user any warning and it dosn't show the content of the email.
Kmail should show the email like it has done in earlier versions.
Operating System: Fedora 31
KDE Plasma Version: 5.16.5
KDE Frameworks Version: 5.64.0
Qt Version: 5.12.5
Kernel Version: 5.3.15-300.fc31.x86_64
OS Type: 64-bit
My workaround is to save the email to a file and open it by Kwrite.
By the way KWrite can even open emails saved to a file larger than 25 MiB.
*** This bug has been marked as a duplicate of bug 387061 ***