[mostlysimilar]

For the government employees only allow .gov domains and verify email.

For people... maybe require a small temporary credit card change with a billing address matching their inputted zip code?

[CarlosD]

This is great, thank you, these seem like the solutions with least technical overhead for me.

I imagine the credit card charge may introduce UX friction, so perhaps we can also allow users to provide a picture of mail with their name and address.