Hi,
yes is possible. The destination URL can be on a different domain. Also since ReDJ 1.5 you can build dynamic destinations, so you could (as example) redirect all URL from a category on the source old site, to new domain. There a good tutorial about ReDJ available in download section with a lot of example.
Let me know if you need more help (send me some example of old and new url).
Regards,
Luigi