User can receive Flip it cab via email

[Deltatristar500]

Hi, my cousin just got a Diamond Touch from Sprint recently and I setup his email on his phone. He uses comcast. He can send emails and a recieve emails, I have sent him some cabs and he is able to get them, however when I try to send him my flipit application cab he never gets it. I have renamed the file to different names just in case it thinks its junk or spam, but nothing. I cant figure out why he can get everything else, yet he can get this 60K file.

Any ideas?

thanks

He has a Sprint Diamond (stock)