AT&T is actively trying to prevent the use of SwirlyMMS and other similar applications on their network when using the iPhone.
The reason everyone is having trouble is because AT&T is denying access to the proxy server(wireless.cingular.com:80). Each request is responded to with "403 Forbidden"
I did have SwirlyMMS working twice today for two very short periods of time until the next polling period and AT&T discovered that I was still using an iPhone. I've done everything suggested here and I give up! Now I'm investigating ways to get out of paying the early termination fee so I can switch back to T-Mobile.
On my very last call with them I had them remove the iPhone Data plan, and the Unlimited Messaging plan, and replace them with the MediaMax Unlimited plan ($35/month and includes unlimited SMS/MMS). This is actually a much better deal. Instead of $20 + $30 / month it is now $35 / month
After I did this MMS messaging worked, when I tried it use it again later it was no longer working. I logged into http://wireless.att.com and it showed an iPhone again. It seems to me so long as it says iPhone on that page you are denied access to the wireless.cingular.com:80 proxy server.
I see several people here are reporting that they have it working. I'm wondering if it worked for their test MMS messages and now no longer works.
I'm now at war with AT&T. Does anyone know if they terminate your account due to "abuse" if you still have to pay the early termination fees?
AT&T makes T-Mobile look like Jesus!