I have a number of users with large mailboxes (20,000+ messages) who are experiencing issues opening and using Outlook. I have asked them to reduce the size of their mailboxes (which they say they cannot do) and increased the resources available on the mail server (a Windows 2008 64bit VM). Apart from implementing a archive policy, is there anything else I can do to alleviate this problem - they access their Outlook client through Citrix PS 4.5. Any help would be appreciated.