If not, this is a serious issue and should be fixed.
However I don't really agree with the word "serious", don't hesitate to submit a wish at
http://bugs.kde.org .
As a question, what's the distinction in Kmail between an "account" and an "identity"?
An account contains technical details about sending and receiving mail. The identity is a composition of your personal details (name, email, organisation, signature, etc). Per identity you can define which server to use for mail. But you can attach identities to folders as well. When you start composing a message in a particular folder (say "KDE"), it will use your "KDE Identity" if this one was set up. Identities are to be configured in the folder properties.