In recent KDE updates, the PIM suite (kmail, kontact) is ...uh... not really working for me. I don't know if it is truly broken or just requires a different approach and understanding.
This has me temporarily using Thunderbird for mail until I can get back to using my beloved kmail. Unfortunately, Akonadi, the engine behind the PIM suite, still insists on going out and fetching mail and doing other things.
Martin Schlander has put up a great post on how to disable Akonadi and I haven't had any messages pop up after following the steps he lists.