[Evolution] how to import old evolution inbox into new account

[kdsfinger gmail com]

hi, all
I used the evolution for 1 year and recently changed my account. By
doing that, the inbox of my new account overwrites the inbox of my old
one. (I may made some mistake somewhere). Fortunately, I copyed the
inbox of my old account to another dir. My question is, how can I
import those old emails into my new account? I tried to copy the old
inbox and overwrite the current one, and I can read those old emails.
But after I connect to the mail server, the content in the current
inbox is overwritten again. If it is not feasible to put them in the
same account, how can I use a folder to display those old mails?
Thanks for help.
zl2k