BTW most email services allow for file attachments anyway. It is just a matter of size limits. They are usually too low for sending whole projects but there are ways to circumvent this. Like compressing (zipping) the files and sending them out in sections. Your waves should have time stamps on them so even if you only send them a couple at a time with the correct import options on the receiving end they should load into whatever DAW the engineer is using.
That is a pain for all involved though.
If that or g-drive isn't suitable then I'd say dropbox.
But be aware even though the site REALLY tries you to get them to install their uploader software it is not necessary. Don't install it. You can just log in and use their online uploader instead. Their local app may seem convenient but I find it is intrusive and slows down the computer. With the wrong/default settings it will always be probing around for updated versions to "backup" your files.
That said... set up correctly it is cool in a way BECAUSE of that. It's like having an external drive except the data gets stored online and it creates a folder on your desktop where you can just drag things to and it will upload to your account automagically.
You also have Gobbler that is integrated with Sonar X3 which kind of does the same thing but directly from Sonar. I have not set up or used it yet though so you would have to ask someone else about it.
Cheers.