e-mail attachments

I have rec. e-mail with attach. that shows 5.7 jpg,(this is document file)
from a mac user and this was a forwarded message. I could not open the file
after it was downloaded. And whoever else received this e-mail, aol user or
others where able to open the e-mail. This has happened before from the same
person- an e-mail attached (picture)that was forwarded to her and she in turn
forwarded the picture to me. I was not able to open this e-mail either. I
spoke to AOL and they said the file was too small for a jpg file. I didn't
understand what they meant. In either case others were able to open and not I.