Compressing video files to send via yousendit
 

I'm trying to send a load of movie files to a friend of mine via yousendit, and I really need to find a way to compress them big time otherwise it's just going to take too long. Zipping them just doesn't do it enough. They are .mov files and the description of the file says the codecs are DV Pal (they're for a film that this friend is editing at the moment). We can barely afford to lose any quality but I was wondering whether it would be possible to compress them to a ****** quality format and then convert them back to a better format once they've arrived?
If not, what's the most I can expect to compress a file without losing quality?