Thunderbird space clean up after accounts removal

I am testing speed of several dovecot servers with thunderbird client in Win7. Each testing accounts have 800M Email . However, everytime I remove these testing imaps accounts in thunderbird , the space it once taken up does not freed up for me .

It turns out that I need to clear IMAP Cache in file explorer after removal of imap accounts in Thunderbird . To manually remove those IMAP cache, check the path of imap cache with your other undeleted imaps accounts by going to Tools -> Account Settings -> Select “Server Settings” ->
and then check for the path of “Local Directory” :

With reference to above screenshot, dig into {Windows USER PROFILE}\AppData\Roaming\Thunderbird\Profiles\d1wlkutf.default\ImapMail\ and check the for the corresponding directory for your deleted accounts and then remove it by hand.