Bug 419298

SUMMARY
I receive daily log mails from our servers. These text-only mails have a large body of text (> 3Mb). These messages fail to display in KMail. That is, they appear in the list of mails, but when clicking the mail the preview window will only show the smart header (subject, from, to) but the message body remains empty. The same goes when opening the mail in a new window (by double-clicking) the mail header in the message list). I can reproduce this both on Fedora 31 and Kubuntu 18.04 with the default installations of Kmail.


STEPS TO REPRODUCE
1. Find a large text-only mail in one of your mailboxes. Mine are > 3Mb of text
2. Click on the mail in the message list

OBSERVED RESULT
Preview window will properly show the header info (subject, date, to, from,...) as with all other mails, but the message body is not displayed. That is, the rest of the preview window is just blank.


EXPECTED RESULT
The message body is also properly displayed.


SOFTWARE/OS VERSIONS
Linux/KDE Plasma: Fedora 31 and Kubuntu 18.04
(available in About System)
KDE Plasma Version: 5.17.5 (Fedora) and 5.12.9 (Kubuntu)
KDE Frameworks Version: 5.66.0 (Fedora) and 5.44.0 (Kubuntu)
Qt Version: 5.13.2 (Fedora) and 4.15.0-1076-oem (Kubuntu)
KMail Version: 5.11.3 (Fedora) and 5.7.3 (Kubuntu)

ADDITIONAL INFORMATION
I can open the same messages with no issues in Thunderbird.