This is an unofficial Terraform module which creates AWS Route 53 records to setup a domain with FastMail.
In your Terraform file:
resource "aws_route53_zone" "example" {
name = "example.com"
}
module "example_fastmail" {
source = "github.com/bluk/terraform-aws-fastmail-dns"
domain_name = "example.com"
route53_zone_id = "${aws_route53_zone.example.zone_id}"
}