I've searched around but haven't found any solutions to this.  Hopefully I haven't overlooked anything.

I have a folder on my imap account (spam) with 8500+ messages in it.  I can't for the life of me figure out how to get roundcube to quickly open that folder. 

At first I thought I might need to replace my imap server.  My imap server is courier (I love it), but I've also copied the same folder into dovecot and dbmail without any differences.  From what I've read both of the test servers I've tried should have benifits but as they haven't I've ruled out that as a solution for now.

I've also tried various imap clients.  RoundCube of course, which takes (guessing) 30+ seconds to open the folder.  Navigating away and back to the folder takes another 30+ seconds to open it again.  That seems riddiculus but Squirrelmail 1.4.x seems to have the same issue. Thunderbird seems to take 30+ seconds to load all the headers but once they are loaded I can quickly move back and forth between folders.  Finally, Squirrelmail 1.5.x works wonderfully - it loads in a second and I can pick an set of messages (page 500 for example) and it will immediately open to that set.  That would be great if I was still using Squirrelmail, but RoundCube is miles ahead in the look and feel.

Are there any current fixes or tweaks I can use for this?  I see two ways to improve this, the first is caching of message headers like Thunderbird apparently does. I could be wrong but I think all that is currently cached in the database is messages, not headers.  (Database and Imap and Apache are on the same machine btw) That would be acceptible to me as once I have my client open it stays open for hours/days.  The ideal fix though would be to impliment whatever is in squirrelmail 1.5.x.  Now obviously that's a perl vs php but it should translate just the same.  If they can do it, roundcube could do it, no?

Thanks,

Jim