Hello!
How many times have we kwallet users tried to save the passwords of our kmail accounts, only to be prompted to enter them all over again after every reboot!? Well, our days of woe have ended, as I've finally managed to come up with a solution to that and to condense it into a 10-step guide for permanently disabling kwallet interference in kmail. To avoid double- and cross-posting, I'm just giving you the link here:

My 10-step program to make kwallet behave and stop messing with your kmail accounts - LinuxQuestions.org

Happy kmails to you!