email archive across IMAP (copy+delete) but zimbra directory not reduced
I use Zimbra since 2010 and I backup it with the full snapshot and zip method.
The Zimbra directory constantly growing and I would like to reduce it with archive all before 2011-12-31 email to another IMAP server. I copy all those email and delete it with IMAP commands from Zimbra, it's about 30G mail, but the Zimbra directory size not reduced .
In Zimbra web client those emails disappeard, (in Trash and in Recover deleted items too)
What should I do ?
Tx for any help.
My Zimbra - 7.1.3_GA_3346.DEBIAN5_64 DEBIAN5_64 - /opt/zimbra is on ext3