When emailing a photo to my SpamCop WebMail from my IPhone (via my Yahoo.com email) the email arrives but no photo arrives.

When I email a photo to my Yahoo.com email account, the photo arrives.

When I email from my Yahoo.com to my SpamCop WebMail account, the photo arrives.

Any idea why emailing from my IPhone to my WebMail account fails to attach the photo?

The question posed doesn't seem to match the scenario described. From your description, it would seem to be an issue with the way Yahoo decides to handle your "to-be-forwarded" e-mail. How do the MIME header lines and body components look, as cmpared to what Yahoo 'saw' and what Yahoo 'delivered' ????

How do I view these?

Easy answer would be "View Source" of the e-mails. The MIME Boundary Lines are defined in the header, then used to'set-off' each different section of the bode .. the plain-text, the HTML, the attached file, etc.

Perhaps there's a bit of a need for more of an explanation of just how you are trying to do what you describe .. For insctance, you stated "emailing a photo to my SpamCop WebMail from my IPhone (via my Yahoo.com email)" .... but then later state "email a photo to my Yahoo.com email account" .... what is actually different between these two actions? I think what I'm not quite understanding is why AT&T isn't involved in your description, followed by the apparent missing step in just how the "via Yahoo.com email" is configured.

For example, is the issue actually at the "upload the attached photo" to the Yahoo e-mail server moment, based on the scenario of you being logged into the Yahoo server and attempting to compose the e-mail on-line ...?????

Another classic Wazoo answer.

I do know how AT&T comes into the equation, but wow, it is amazing how troubleshooters work!

Miss Betsy