Ok, I found my problem,
I run a backend IMAP/POP3 Server (DoveCot) with a front end IMAP/POP3 Proxy Server (DoveCot). I found that the proxy server was not advertising the fact that it supported QUOTA's. Once I enabled mail_plugins with quota support for the 2 protocols it all worked.
Is this correct for a proxy server config. I have included my config below for comments?
################################## base_dir = /var/run/dovecot/ protocols = imap pop3 disable_plaintext_auth = no shutdown_clients = yes syslog_facility = mail ssl_disable = yes
login_process_per_connection = no login_processes_count = 5 login_max_processes_count = 128 login_max_connections = 256 login_greeting = POP3/IMAP Server Ready.
protocol imap { mail_plugins = quota imap_quota }
protocol pop3 { mail_plugins = quota }
auth_cache_size = 16384 auth_cache_ttl = 1800 auth_verbose = no auth_debug = no auth_debug_passwords = no verbose_proctitle = yes
auth default { mechanisms = plain
passdb sql { args = /etc/dovecot/sql.conf }
userdb static { args = static uid=1000 gid=1000 home=/dev/null }
user = root count = 1 }
plugin { quota = maildir }