The RUS sets e-mail addresses automatically. So basically there is not much to backup there. But what about the other e-mail addresses, the ones that are manually set? Microsoft posted a nice script doing just that, so you can backup and restore (using the handy Ldifde utility) all your e-mail addresses, including manual ones. It look very much a like the one that I wrote a while back (one of my first articles), but with LDIF compatibiliy.
For more info and the script: