Hi,

I use Dovecot 2.3.9.2 as IMAP proxy for other mail server and configure it with imapc_host/imapc_port/imapc_user options. All works fine exclude quota information.

Although my IMAP server supported quota Dovecot does not relay it to users.

As I read in docs/MailboxFormat.imapc.txt in Dovecot v2.2.30+ there is a way to relay quota data to end users:

Quota
-----
Using the "imapc" quota backend allows asking for the quota from remote IMAP
server (v2.2.30+). By default it uses GETQUOTAROOT INBOX for getting the quota.
There are also two parameters that can be used to control how the quota is
looked up:
 
 * box=<mailbox>: Use GETQUOTAROOT <mailbox>
 * root=<name>: Use GETQUOTA <name>

 For example:
 
 ---%<-------------------------------------------------------------------------
plugin {
  quota = imapc:root=User Quota
 }
 ---%<-------------------------------------------------------------------------