I know i have to lose quality in the photo, but that's not important to the task ahead, the question was technical, not practical.
All my previous phones reduced the photo to MAX MMS supported size, no matter what, i didn't had to use any external tool or manual process, just attack, auto resized, send, easy as pie.
There must be some hidden configuration that tells the phone to do this, all i need is to set that value properly.