Well I don't use the X700, I use the X800 but it is similar in system... I don't see where or how we could store all the incoming/ outgoing (draft/ sent) by default on the mini SD card... all we probably might be able to do is move the folder we saved them all in (in the phone memory) manually to the mini SD card. Select inbox, mark all you want to save, copy/ move to the new folder you created in "My Folders"... but after that how do we even copy/move that new folder onto the SD card???
There is a program availble that actually lets you do this, its called MsDriveE. its very hand because even when someone sends you a file via bluetooth or infrared it goes into the inbox, but now you can receive large files to into your inbox. You have to start up the program again everytime you turn off your phone though.
And there is a little cpeciality about this MSdrivE. If you install it just right form your inbox, it'll do you no good. You must first copy/cut and paste it ON YOUR FLASH CARD and then install. Installation must be only on your card, not the phone memory. And other thing is that you will have no access to the phone memory after the instalation of msdrive, until you reboot the phone. That was what i've heard about this thing.