Thanks to both gentlemen who answered, but the problem still exists. I tried all the suggestions that were made without success. There's just got to be a way to do this. Macs not being able to do anything Windows can do just seems wrong.
We can not help you without more information.
Please describe step by step how you are attaching the photos. In particular, please tell us the exact file name of the photo you are attaching. Also, please let us know the domain of the person you are sending us to. We don't need to know the entire email address, but the part after the "@" is helpful.
Also, can you explain what problem the recipients are having? Do they see an error message? If so, what does the error message say? If you know it, can you tell us what email program they are using?