Sorry - I meant the "receiver" tells me the file is corrupt and not the sender. Please allow me to clarify. Thanks!
Close your project and then open the file you are sending to ensure it opens okay, you could test in Photoshop and any other apps that open jpeg's
After ensuring it opens successfully try sending it to them in a different way other than Dropbox, you could use Creative Cloud for example.
Upload the file here, set it as public, share it with them via email as an alternative
Welcome, hope it helped