You might try asking about this on the Courier IMAP list: http://lists.sourceforge.net/mailman/listinfo/courier-imapYour problem's not really specific to Sparc (or even Linux), and you're probably much more apt to get a good answer there.
Jim Crilly wrote:
The problem now is that on the really large mailboxes (the cut off seems to be around 9K messages) the sort capability causes problems with IMP because ittakes so long.