chances are: checks it against a database of addresses it has seen before (e.g. because they were used to register stuff elsewhere). No such entry, or entries all younger than n days -> 'freshly registered'.
Sucks for people who don't use their addresses for just about anything.
It is not a healthy idea to prevent access to a trial solely because of a lack of reputation associated with an email. However, in this specific case, if there is a rotation of numbers at the end of the email, tirreno has rules that detect similar email patterns.
Additionally, I assume that registrations are coming from the same IP or network, which should make it simple to detect through platform.
Sucks for people who don't use their addresses for just about anything.