How to ensure mailbox user deleted when delete their account from zimbra admin

[nyomanjs]

Dear all,
when we delete a user account from zimbra admin, that delete mailbox too? Because in my case space /opt/zimbra still big even i have delete some user with big size.
Usually i check their mailbox size with :
su - zimbra
zmprov gqu `zmhostname`|awk {'print " "$3" "$2" "$1'}

TiA