TIL about emaillistverify. Their website always talks about „bulk email checking“, but I assume they also support „live checks“ through an API?
I assume you prevent users from signing up if the check fails?
So presumably yes
I’d look into fingerprinting (https://github.com/fingerprintjs/fingerprintjs), block by ASN if it makes sense for your business (does OVH really need access to my SaaS?), use an active disposable email checker and possibly flag risky orders for manual payment capture if at all possible.