Go to the host OE, and click on Tools, Options, and the Maintence Tab. There you will find a button for stores. That is where all the DBX files are stashed which are the mail and boxes. Copy that entire folder to the other computer's corresponding location and all the mail will be there as well.
There is an export-import function, but that gets too screwed up and complicated.
BTW . . . use that Stores tab to put your OE mail anywhere you like. I keep mine on a removable high capacity disk. (LS-120. Zip will work . .. Syquest or what ever.)