I'm going to answer this from another angle. Sending large files should never be a problem in these days of fast storage and fast connections. You don't have to crunch down that file size at the risk of degrading quality.
While there are many services around, I like Dropbox.com it integrates on the Mac and PC. You would place the file or files in the public folder and email the link. If the files are confidential, archive them in a password protected zip file.
Adobe also has file sharing services if your clients are Adobe customers.
Either way you can upsample and should not care about file size.
Gene