Full email integration with vBulletin

How hard would it be to fully integrate email with vBulletin. This would allow the members using a board to respond to eachother either by email or on the web.

Similarly, when someone replies to my message, I see their entire reply, not just "so-and-so has replied to your message."

This feature would lower the barriers to participation and make our discussions more active, more live.

However, the benefits of having the discussion on the web, such as having a visual chronicle of a conversation and having everywhere-access, would still persist.

Any recommendations? I'm trying to pick a package to build on, and I'm also considering UltraBoard2000.

Thanks,

Paul