Oh no i hit the wrong button! After i clicked on 'Rebuild', everything is gone! They are messages residing in an expired email server, so i can't retrieve them anymore!
AHHH!!! It's really sad. All my work emails are gone.
Why doesn't apple mail have a function that ask me to confirm whether do i want to 'rebuild'.. After i accidentally click on it, everything is gone, i was dumb folded!