Although my settings are correct for MMS, T-Mobile is experiencing an outage and therefore all phones, whether it be an iPhone or not, cannot send any picture messages. T-Mobile is currently working on the problem and have not released an estimate of when it should be fixed. Atleast that's what the lady told me.
EDIT: Nevermind! MMS works now for me!
EDIT: Nevermind! MMS works now for me!