...hmm. not easy..
video 'eats' disk space... for sure, you can compress video, but all those codecs (divx, h264, ...) are for playback, not meant for editing... you could mail such files, but when you convert them back into something useful for editing, you realize a dramatic loss of quality...
best practise is, what Roy told you, to use 'snail mail' and deliver data-dvds (even those could fit max 20min of editable material ...) or miniDV tapes...
iM can handle mpeg4... but that is again a lossy codec. ...
if you're owning QTpro, you could use the more efficient codec h264, ...
.gvp is Google's own codec/'standard', only in use with the GoogleVideoPlayer...
yousendit.com allows attached files of max 2GB ... that is in 'dv', iM's native codec, 10min 😉, but in h264 you would share a lot more...
keep in mind: iM is for TV-delivery... 720x480/30fps/interlaced.. ANY other res, fps, codec... will result in loss of pic quality (e.g. youtube videos have a quarter of res!) ... if you use h264, try to keep the res and framerate ...
in recommended order: miniDV tape, dataDVD 'dv', dataDVD h264, yousendit et al ...