Hi,
Firstly dvd video files are huge (several gigabytes) so your email provider may not allow you to send such a large file. Secondly it will take ages even at broadband speeds to upload and download, if you or the recipient are on dial up forget it. You will be better off putting the disc in the post.
What you need to do is run the dvd through a ripper prog to de-code the files into avi or similar mpeg2 these files will play on virtually any computer. dvd shrink 3.2 will do this if isn't encrypted (off air tv or home made dvd) if not you'll need to decode this using dvd decrypter first then use dvd shrink. Both these progs are freeware. If you wanted to save space you could rip and re-encode using Divx (mp4)or similar (Quicktime or Real Video) which is highly compressed so saving some space.
http://www.dvdshrink.org/
http://www.dvddecrypter.org.uk/
This site has lots of info and more links to rippers and what you can do with dvd files
http://www.doom9.org/