Actually the contract is in place when the order is confirmed. At least from EU webshops it's common to receive two mails, one for order received, another for order confirmed (potentially hours or even days later).

This actually hit the spotlight recently in Spain as Dell advertised 1000-1800€ laptops for 29-35€ on their site[0]. Many people bought, received the first AND the second email around 5h later.

If it wasn't for that second email, they could cancel the order no questions asked, but actually someone on their side said "yep, this order looks fine" and clicked confirm. Consumer associations are hitting Dell with all their force.

[0] In Spanish: https://www.eldiario.es/tecnologia/portatiles-Dell-clientes-...