I quite often experience that when I go to my inbox folder, where the messages lands when fetched from my pop3 account, some messages from last fetching is copied. They are messages that were moved to an other folder by a filter upon arriving. These messages are then marked as unread, since the new copy is not read. Sometimes some spam messages are recreated in inbox. Reproducible: Sometimes
Same, but happens to me all the time with spam mail. Using 4.9.2
I think this issue may be on the radar of kdepim developers :)
This should be fixed in master and latest 4.9 branch
Thank you very much! Looking forward to next updates :)