I spoke with the Alltel data tech. reps. and they told me that the 6700's hardware does not support MMS. Later that day, I called a different set of people at Alltel and they told me that I can run my own MMS server and send/recv. that way. Other reps. told me countless times that even though I'm running Windows Mobile 6, my 6700 will never do "true" MMS, and that I should upgrade to the 6800. Using the following configuration, I'm able to get pictures (very small size) directly to the handset, and video is sent to axcessmypics.com. I cannot send any type of MMS, however.
Server name: default
Gateway: <blank>
Port: 80
Server address:
http://mms.alltel.net
Connect via: Alltel Wireless
Sending size: 350K
WAP: WAP 2.0
Matching the 6800's configuration at my local Alltel store was difficult because it was running Windows Mobile 5! Ouch...
Still waiting for someone to figure it out.