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Once you feel you have good control of the serve then you can develop this to hit the serve as you move to the T position from the service box.
You have to make sure you keep one foot inside the service box in contact with the floor when you strike the ball.
This still shows that this service is very close to a fault with the back foot just coming off the floor at the ball contact point.
More obvious cases of early T encroachment will give the opportunity to some referees to call a service fault. It is a silly point to give away.