I’ve had a lot of questions regarding my Profiles and MMS Settings.
At the moment it is not possible to set MMS Settings via the Profiles. It may be possible under IOS5 but Apple have not released any information as of yet if you can. (But I don’t expect so).
If you can enter the details in my hand you can go to the Mobile Settings section of the website and it will give you the settings but if you cannot then you are stuck.
There are a number of jailbreaks available to make the settings editable but I have no idea which ones actually work and I cannot (at the moment) suggest any.