Outlook 2000 and 2002 ANSI size limit of 2GB. Unicode format size limit of 20GB for Outlook 2003 & 2007 and at least 50GB for Outlook 2007 and newer.
Internet Evidence Finder (IEF)
Trial available with access to full product functionality for 30 days.
They also have a range of free tools
Kernel Outlook PST Viewer
A free tool to open, .PST files without needing to install MS Office Outlook. Limited trial versions available.
Kernel Data Recovery have a large selection of tools for managing Microsoft Office and Exchange. Interesting data recovery tools.
Offers all kinds of information on MS Exchange, including info on email Forensics in a Corporate Exchange Environment.