sync_server is only updating the bottom 32 bits of quota_mailbox_used (stored in network byte order) at the moment. Here is a fix:
http://www-uxsup.csx.cam.ac.uk/~dpc22/cyrus/patches/2.3.8/sync_quota.patch -- David Carter Email: [EMAIL PROTECTED] University Computing Service, Phone: (01223) 334502 New Museums Site, Pembroke Street, Fax: (01223) 334679 Cambridge UK. CB2 3QH.