I have the same problem.
Found this bug report for Fedora:
https://bugzilla.redhat.com/show_bug.cgi?id=1422626
The Workaround also works for me:
1. Load Kmail
2. Hit "Settings->KMail"
3. Press OK (no need to change anything, just hit OK)
- After this the settings appear to reload.
regards
Markus Köberl