There are only two free and trustworthy VPNs; windscribe and proton. The former has a limit of 10 Gb. So, which VPn are you planing to use? Why is TOR not secure in this case?
Besides, having a high level threat model and using email for communication are inconsistent. Why will you need to use email for communication instead of secure messengers?
This would be a very very niche case such as being a whistleblower or sth like that, and you only have an email address and no other way of communication.