Hit ENTER after each Tag to add it to your post; Numbers in parentheses represent the Tag's usage.
I'm using Thunderbird with the "Display Quota" AddOn since years on the cyrus Mailserver. This is working very well, and I see the mailbox usage right in the Thunderbird interface.
I switches with one account now to Smartermail and it looks like, Smartermail IMAP lacks on QUOTA Information. Does Smartermail not Support rfc2087 ?