When serving in squash, you MUST have one foot inside the service box. The service box is the square on both sides of the court. The short line, is the line that goes from one sidewall to the other. This line indicates where the service box starts, but also is used for where the ball must bounce (I’ll talk about that in another article).
If you don’t have one foot inside the service box when you serve, then that is a foot fault.
The reality is that for referees, it can be quite difficult to see if a player really does have their foot inside the box as they make contact with the ball, and the reason is that smart players are walking towards the T as the hit the serve.
The second question might be “Why are smart players walking towards the T when they serve?” and it is a good question. Fortunately the answer is simple: You should be on the T BEFORE your opponent can hit the service return. Too often, club players serve, stand, watch and THEN react to the service return.
Not only should a good serve make it difficult to return well, your movement should also ensure that whatever type of return is made, you are able to reach it.
For right-handed players, moving towards the T when serving on the right-hand side of the court is best done by serving with a backhand shot, again, more on that in another article.
The key is to make contact with the ball with you foot as close to the line, but not touching it, as possible. That way you are close to the T without breaking the rules.