MMS Server response error - Possible Fix!
I've ready through and tried all of the "fixes" for the MMS but to no avail. However, after having read through many other sites, I discovered that it might be as simple as re-listing your contacts' phone numbers so that they are only 10-digit strings. For example: My phone number should be listed as 13032045999, not +1-303-204-5999, nor 303-204-5999, nor 303.204.5999, etc. Get it?
Try resetting the listing you're having difficulties sending an MMS or SMS to, and give it another try.
This might also help with syncing your contacts with your Gmail contacts online.
Stock everything else