Please note that one should not replace the new kmailrc file with an older one. This causes all new emails to have sender, subject and date set to "unknown".
I noticed this while migrating from Kubuntu 8.04 to 9.10 (KDE3 to KDE4). Running Kmail 1.12.2 now.
I do not know if any of the above applies to other 'unkown sender' problems. But of course one can test: if no other solution works, try to rename ~/.kde/share/config/kmailrc to force regeneration of this file.
Please note that one should not replace the new kmailrc file with an older one. This causes all new emails to have sender, subject and date set to "unknown".
I noticed this while migrating from Kubuntu 8.04 to 9.10 (KDE3 to KDE4). Running Kmail 1.12.2 now.
I do not know if any of the above applies to other 'unkown sender' problems. But of course one can test: if no other solution works, try to rename ~/.kde/ share/config/ kmailrc to force regeneration of this file.