KMail local folder

I have a large amount of old emails in /var/spool/mail/tim/ on my laptop. I have created a KMail account specifying the MBox file /var/spool/mail/tim/. I have chosen Lock method: None I found there was already a Local Folders account pointing to a Maildir folder at ~/.local/share/local-mail which in fact is empty. So I called the new account alice (the email comes from in.alice.it). Unfortunately after setting up the MBox account as above I do not see the email in the /var/spool/ folder. It is clear that I do not understand KMail accounts properly. Could some kind soul please enlighten me. Should I perhaps delete the old "Local Folders" account, and use this name for the new account. Or is that irrelevant?