chore: add mx verification record for custom domain (#221)

Author: j4y

terraform/website/dns.tf

@@ -1,5 +1,12 @@
+# domain verification with Microsoft
+resource "aws_route53_record" "mx_verification" {
+  zone_id = data.aws_route53_zone.main.zone_id
+  name    = "@"
+  type    = "MX"
+  ttl     = 3600
+  records = ["10 ms21173179.msv1.invalid"]
 
-# TXT record for domain verification with Microsoft
+# domain verification with Microsoft
 resource "aws_route53_record" "txt_record" {
   zone_id = data.aws_route53_zone.main.zone_id
   name    = "@"