When KMail set to archive to a yearly folder, it archives messages based on the current date, not on the message's date. Reproducible: Always Steps to Reproduce: 1. Set up the IMAP account to archive messages to a folder named after a year. 2. Archive a message from last year. Actual Results: Archival is done based on current date. Expected Results: Archival should be done based on message's date.
There should be a way to choose whether to archive by current or mail date. I personally think it makes more sense your way, but it should be configurable.
This is still an issue on kmail 5.8.3 on Fedora 28.
This is reproducible with KMail 5.10.2 in Chakra.
Still present in Version 5.24.4 (23.08.4).
I work on it at the moment. Regards.