How?
There is no contract between the victim and the email provider. Any contract is between the provider and the account holder and I am sure that there is a clause allowing the provider to suspend accounts if the TOS are violated. There is in any case no guarantee of delivery of email.
Advice is never, ever to pay the ransom, on the basis of Kipling’s verse:
“I tell you again and again
That once you have paid him the Danegeld, you never get rid of the Dane.”
