Trawling the internet for a fix to this problem for 6 months now has still not resolved the issue.
I have an iPhone 4s, on a pay monthly 02 contract. I upgraded to a 4s from a 3gs, which incidentally NEVER had this problem, the 3gs sent MMS pics from day 1 and continued to do so.
Since getting the 4s I have never ever been able to send an MMS or receive one from anyone, regardless of their phone and/or network. I have spoke to 02 many times, depending on who you speak to it's 'Apple's fault' or 'there's a known fault and should be resolved soon' or 'there's not a problem with your MMS settings here'... blah blah blah. Apple on the other hand say it must be a problem with the carrier, or ask me to wait for the next update.... unsurprisingly 5.1.1 hasn't fixed it.
Reading countless forum posts it's obvious that many users on pretty much all carriers have this problem.
I have tried every bit of advice that people have kindly suggested, but to no avail.
This really isn't a cry for help for another solution, it's more a general enquiry (rant) if anyone out there knows if Apple are doing anything at all to resolve this? A simple google search for iphone4s mms should make alarm bells ring for them. My phone cost me a fortune and I can't do what I consider to be a very basic function, yet some of my friends' cheapo-crappo phones have absolutely no problem sending pictures at all. Except to me of course 😉
/end rant