From https://bugs.kde.org/show_bug.cgi?id=259949#c308 4. it appears that at least old installations do not automatically activate search completion, so it must be done manually. It would make sense if eventually broken configurations get fixed on an update. It would be best, if this would be fixed after all problems with autocompletion are solved. Reproducible: Always
Is this still the case? I think it's on now.
This bug has only been reported for versions before 4.14, which have been unsupported for at least two years now. Can anyone tell if this bug still present? If noone confirms this bug for a Framework-based version of kmail2 (version 5.0 or later, as part of KDE Applications 15.12 or later), it gets closed in about three months.
Just as announced in my last comment, I close this bug. If you encounter it again in a recent version (at least 5.0 aka 15.08), please open a new one unless it already exists. Thank you for all your input.