This is done in such a way that milk is spilled in the east direction.
According to vaastu shastra east direction is considered auspicious and it brings luck, prosperity, peace and good health.
So this custom must be done to activate the flow of energy in east direction to bring good luck and prosperity.
East is also the direction from where sun rises. thus by spilling the boiled milk in east direction we are trying to make an auspicious beginning in our home.
Agenya is good for Agni. He is the ruler of Agenya mula. So we will have our kitchen in this corner only. To satisfy the Agni and pray him to see that we will be happy and well with in the new house without any accidents or untoward incident for the family in the house.
It is the belief of people that if we allow milk to over flow in new house, we will have a very happy and prosperous life.
A blunt knife or rusted knife can't be useful for anything just for the sake we call it as the knife similar to PayTM series or Sachin or Virat records.
Milk is spilled over purposely in house-warming ceremony i.e 'grihapravesam' as it signifies that the residents (actually owners) live in prosperity as mentioned by Dr.Rao gaaru. But when the same is spilled over on normal days, it is considered as a sign of wasting of wealth. As no one wants to waste their wealth (money), they are very cautious about spilling of milk on normal days. There's nothing danger in it if milk overflows due to forgetfulness or some other reason. Practically, it becomes difficult to clean up the stove and the burners. It gives out a charred smell also which is not pleasant.
Spilling over of milk on Sundays is allowed. I have mentioned whatever knowledge I have on this and there is no scientific proof of the same. It's just a belief.
Thanks & Regards
'Idhuvum Kadandhu Pogum "
Even this challenging situation would ease