Just once in my life I've done the Google search in advance, done the changes, and thought I'd solved the problem... but it didn't work. So...
I got my o2 iPhone 3G unlocked by o2, and I gave the phone to my wife, who now loves it. She wants to be able to send me snaps of the kids, so she asked me to try and get the MMS set up. So I duly did that, following the instructions here for t-mobile users.
I used the instructions here:
http://blog.flashgen.com/2009/06/18/enable-mms-on-unlocked-iphones/ And lo and behold, the settings seemed fine after that - I got the little camera icon next to the text field in the SMS app, I got the send MMS option in the photos themselves, and so forth.
So it all seems fine, but when I send her an MMS or she tries to send one to me, no joy.
Any advice?
Yeah yeah, I know: "Google it".