One daughter has an AT&T 3GS the other one has a jailbroken/unlocked 3GS with a T-Mobile plan. Both are on 3.1.2

When she picks a photo the "regular" 3GS has 4 menu points: email, contact, wallpaper and MMS. The jailbroken does not have the 4th option. Is there a way to also enable the jailbroken iPhone to send/receive MMS?
I found a page (help.benm.at) but after adding the information provided there nothing seems to have changed.

Another thing: when daughter one 1 sends a movie (.mov) she has taken with her iPhone, daughter 2 can watch it but does not get the sound. Could this be connected to the missing MMS capability?

Thanks.
Kraut55

check the last post of this thread:
http://www.hackint0sh.org/f207/111003.htm

and read this thread: http://www.hackint0sh.org/f207/93057-18.htm
Make sure you read the entire thread.
I don't have tmobile so I can't tell you if it will work or not.