Probably the Date: header of these messages is broken and & kmail; cannot interpret it. That is not a bug in & kmail; but in the software that sent the mail.
Probablement la capçalera Date: (data) d' aquests missatges estigui trencada i el & kmail; no pot interpretar- la. No és un error del & kmail;, sinó del programari que ha enviat el correu.