[ Thanks to Sensei for this link.
“One problem I had with Kmail was that I share an account
with my wife, so how could we both see the mail if we logged on as
different users and downloaded our mail at different times?
Sound confusing? Basically, I needed to set up Kmail where we could
both see all the inbound mail and filter it to our own inbox.”
“Here’s how I did it:
(1) Add a folder by selecting Folder >> Create, for each
user. I named it after the user(ie.. “From User”), but you can name
it whatever name you like.”