I know tweaks2k2 can do this for you, but when I tried it, I ran into problems with my SD card. After applying the change, it seems the SD card loaded AFTER whatever changes were made to put the emails onto the card. I found this out because I had a Storage Card and a Storage Card 2. The 2 was the actual card and the regular one was just a directory with my email.
Check out Tweaks2k2 at
http://www.tweaks2k2.com/. Please make sure you do a backup prior to fiddling with anything!