For my new/old laptop I decided to go with a KDE desktop; it's been 10 years. Also, I've been seeking to get away from the ridiculous reliability and boringness of claws-mail, because I almost kind of don't trust a thing that runs so well for so long; claws-mail, I loathe your perfection.

Already using Kmail I got my wish, heh. All new emails are going into the trash folder. They are directed to go into the inbox folder, as configured in setup for each email address.

This is on a fresh sweet, sweet Debian Wheezy install. I only have set up one filter thus far, for local root@ mail, so it's not that.

Google showed plenty of results, for gmail and other web mail services. Sigh.

Are you using any filters? Also, Debian Wheezy uses a really old KMail (4.4.x, now quite a number of years old) and thus is very hard to spot (and fix) issues.