Once in a while KMail displays a window on startup that says "Filter account is missing". An empty list of accounts to select one is shown. Clicking OK or Cancel seems to remove filter rules from KMail. This is known as Bug 323455. The commited fix was reverted. How to deal with this problem. Is a new fix in sight?

twarnke wrote: This is known as Bug 323455. The commited fix was reverted. How to deal with this problem. Is a new fix in sight?

No idea.

But you could make Akonadi start automatically on login, by configuring "Show Events" in the panel clock's settings f.e.
(the bug seems to only occur when Akonadi isn't running already)

That's how it is on my system, and I never had this problem. I did see it when stopping Akonadi and then starting KMail without starting Akonadi first, but clicking "Cancel" never deleted the mail filters here AFAICR...