FTP server might be a good choice but 500 + of RAW's. Is this wedding retouching or something like that?
If so and he absolutely has to sending it online, I would maybe suggest to send Hi-Res JPEG's and the critical ones as RAW's. Or better yet to the new losssy DNG format. Better than JPEG and much smaller than RAW. Depending on what kind of work needs to be done it could be good option.
Or even better way if he is in the same country, would be to send it via post office as package. You said 500 + RAW's, so that is what aprox 10 MB x 500 = 5000 MB or 5 GB. That can be send by two DVD's for a day or two. Also if he converts them to (lossless) DNG, he might get 30% smaller files all together. Fits to one DVD.
So lets say that what 3.5 or 4 GB. You can send that over FTP server or use two DropBox accounts depending on how much storage you have or you can use something like DropBox maybe GoogleDrive, it can get you 5 GB for free.
Also I like to use https://www.filemail.com/
free large mail service. It offers sending up to 2 GB for free. Maybe send two emails than.