I've gotta start out by saying that this is one of the best plugins out there. I know you here that often, but it is. 
I'm currently trying to use a form with Cforms v. 10.5 and I've gotten just about everything to work. However, when I use the 'placeholder' option to change the AdminTO email address, I have found that the uploaded files are renamed to "25-" "26-" or "Phzx134ma" and such—and no extension. These are PDF and txt files I am currently trying.
However, once I place a correct email address back in the Admin email spot (such as info@example.com) and comment, or disable the my-functions.php, it works again, sending the files with the original name and either .pdf or .txt on the end.
Any ideas?
I've gotten everything else to work and have this same problem with the original code (of course changing the email address):
if ( $setting == "adminTO" ){
if ( $oldvalue=='placeholder' )
return 'test123 <my@different-email.com>';
}