"My mailbox size is 7.4GB. I send/receive around 200 emails a day; so that 7.4GB of email goes back several years. I don't use too many rules so most of my email ends up in my Inbox (30k items).

My background is in software performance (especially storage performance); so I couldn't live with the status quo. I was stuck, I needed my large mailbox; but I also needed a great/fast user experience so I could effectively process my mailbox. All of my machines had sufficient memory (2GB or more) so I couldn't solve the problem by adding memory (to provide the Windows System Cache with more memory to buffer the OST IO's). "

Continued: http://msexchangeteam.com/archive/2007/12/17/447750.aspx

Summary:

1. Make a set of folders containing content that is over a year (or two) old - so that your mailbox size becomes manageable.
2. Separate the content in these folders chronologically.  2004, 2005, 2006, 2007, 2008, etc.
3. Set Outlook not to sync these archive folders to your devices.  While online, you have access to this content; offline, you can't access anything older than 2 years.

This maintains the following:

1. Your large mailbox, allowing you to keep all your email online in Exchange for backup and quick access (via a web browser).
2. No PST usage.  No management of pesky PST files, and you don't have to worry about backup - the Exchange is stored on a RAID set, and backed up frequently.
3. Good laptop/desktop/workstation Outlook 2007 cached user mode experience.
4. Ability to search entire mailbox.  Open Outlook in online mode, or open up OWA.
5. Low processing on the server.  Working in offline mode means that the basic mail processing is done locally on my machine, not on the server.