Tiger Mail Not Working With Imap Server


I have recently updated several client systems from Jaguar or Panther to Tiger. In each case they use the Apple mail.app to access an IMAP server (actually the mail-server built into Mac OS X Jaguar Server). Previously this all worked will. However, Tiger's mail.app seems unable to use the IMAP server. It has difficulty loading the largeish (8,000?) msg-base. Stalls, hangs, sometimes crashes, sometimes duplicates msgs, struggles big time. Are their known issues with Tiger's mail.app? Do we expect fixes from Apple? Are their known ways to coax the Tiger mail.app to handle a large msg-base from an IMAP server?