Incoming mails aren't filtered if the target where they go is not the default inbox. In my case, I have selected a different inbox folder in a different collection for one POP3 account. No filtering is done at all for those incoming mails. When I apply some filter manually, everything works. More annoying, I had some trouble with the standard mail collection on another machine. So I removed the default collection and re-created it (with the akonadi config dialog). After that, no filtering is done at all, even if the mails got to the default inbox. Reproducible: Always
4.10.5 is very old. We fixed a lot of bug in 4.11/4.12 And I use several inbox for my pop3 accounts and filtrering work fine. Please retest with new version.
Seems to be fixed in 4.11.3. Sorry for using 4.10.5; this is at the moment the version marked as "stable" in Gentoo. Sorry for the spam ;-)
Please REOPEN this bug because I have here a full blown regression with Kmail2 ver. 4.12.4 openSUSE packages of the repo: http://download.opensuse.org/repositories/KDE:/Current/openSUSE_13.1/ (with extra repos). Setting: local mail folder, in this local mail folder I have a lot of different mailboxes whereto the mail is filtered. Bug: everything is buggy. I have spamassassin filtering spam even if it is whitelisted. I have incoming pop3 mail that is simply put all in the very same sub-mailbox, no matter what filter should be applied, this mailbox will be random. Filter bar sometimes stays open at 100 percent (hangs). Closing Kmail sometimes help....sometimes not. The filter system is quite useless as it is now. The behaviour is completely random. Bug: filters in POP3 work erratic and wrong. Filters block randomly. Regression. What the program does: well in 2014 we should now be able to filter pop mail. I could give you the filter logs but they are sensitive because they contain of course all the email addresses. The filters run through and at the end the program states: applying filter action and chooses one submailbox as filter rule. Which one that is, doesn't matter to kmail! It is random. No rule or error message in logs. Just at the end, for a specific filter run, the program takes one subfolder it "likes" and puts everything in it. What the program should do: filter the bloody email according to the filter rules given.
And we have also the amnesia-regression. When the filter is loaded, every second reboot one of the filter infos is lost. There is the well known pop-up window that says: cannot find the rules for....and gives you the respective filter name. "Please choose among the ones listed" but the list is as time ago it was - empty. So what one can do is to delete that rule, apply, say ok, reenter, recreate the rule, apply, ok. Then this will work for some time. And then a new rule will be victim of amnesia. All this is a déjà vu of a bug in the earlier 4.x versions after the change of akonadi. Same same.