I don't know of a way to compress video out of AE small enough to transfer via the internet that'll still retain broadcast quality. I doubt Digital Anarchy's Microcosm or any other codec can get full-rez files that small, but maybe. If you can both get access to an FTP site, you can transfer those large files without degrading them to meet a size limitation. Also, I've never used them personally, but I know other editors who do what you're trying to do using services like Whale Mail (http://www.whalemail.com/).
It depends the size you are trying to send. Are you talking a 30 second commercial? Or an entire full-length feature? I know you can send files online up to 4GB with Getalink. I've never used whalemail but I use Getalink frequently and I can vouch for the fact that it works. The address is http://www.getalink.com