In the message list, the name of sender is replaced by the name of receiver for all the messages (in the message view names are correctly displayed). However, this wrong behaviour happens for just one IMAP account, all the other accounts display the message list correctly. They all share the same default "smart" theme. Removing and re-adding the account seems to correct the issue, but the next time kmail is started the problem reoccurs. Reproducible: Always Steps to Reproduce: 1. Start kmail 2. That's all 3.
The smart theme uses a ‘sender’ field that is actually a ‘sender or receiver’ field, where the choice depends on the folder type. It is unclear to me actually how to determine the folder type. Anyway, to solve it, go to View > Message List > Theme > Configure… Then clone the smart theme; give the cloned theme a nice name; in the cloned theme definition's Appearance tab, drag the ‘Sender’ out into the list of fields above (it is actually the sender/receiver) and then drag the real ‘Sender’ in its place (right click to get the option to soften). So in some sense, this bug report is not really about a bug, but about a potentially confusing feature. You can choose to close it or leave it open, but then perhaps change the title to reflect the actual issue (confusing nature/bad discoverability).