Shipping CAP issue

Hello,
I found something weird in every woocommerce website I made.
I explain: when i buy something and I go to the cart, when I ediz the shipping zone, as example “Milan”, and I put a zip code(CAP in italy) different from the range of zip codes in Milan (ex. 71100), it doesn’t tell me I’m wrong and it go on the checkout, like the zip code I put was OK, but it was not.

You can try it here: https://www.queengnails.com/

Thank you anyone.
Gianluca.