The only thing I can guess is that the Bold must have a filter that won't allow you to post JPEGs of unattractive women. I think if you want to have ugly-woman wallpaper, you have to be with Verizon.
Sent it to myself from my Yahoo mail account that solved the problem.
When I send Jpgs to myself from the same e-mail addy on a windows computor they come in as a *.dat file extension.
I try send to self from my Mac and report back later