From f27332614e43b71a14bddcaf36e50afabf11910e Mon Sep 17 00:00:00 2001
From: Julien Dessaux
Date: Tue, 3 Sep 2024 08:42:30 +0200
Subject: added email DNS records unused zones blog article

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+---
+title: Email DNS records for zones that do not send emails
+description: Automated with terraform/opentofu
+date: 2024-09-03
+tags:
+- cloudflare
+- DNS
+- opentofu
+- terraform
+---
+
+## Introduction
+
+There are multiple DNS records one needs to configure in order to setup and securely use a domain to send or receive emails: MX, DKIM, DMARC and SPF.
+
+An often overlooked fact is that you also need to configure some of these records even if you do not intend to use a domain to send emails. If you do not, scammers will spoof your domain to send fraudulent emails and your domain's reputation will suffer.
+
+## DNS email records you need
+
+### SPF
+
+The most important and only required record you need is a TXT record on the apex of your domain that advertises the fact that no server can send emails from your domain:
+```
+"v=spf1 -all"
+```
+
+### MX
+
+If you do not intend to ever send emails, you certainly do not intend to receive emails either. Therefore you should consider removing all MX records on your zone. Oftentimes your registrar will provision some pointing to a free email infrastructure that they provide along with your domain.
+
+### DKIM
+
+You do not need DKIM records if you are not sending emails.
+
+### DMARC
+
+While not strictly necessary, I strongly recommend to set a DMARC record that instructs the world to explicitly reject all emails not matching the SPF policy:
+
+```
+"v=DMARC1;p=reject;sp=reject;pct=100"
+```
+
+## Terraform / OpenTofu code
+
+### Zones
+
+I use a map of simple objects to specify email profiles for my DNS zones:
+``` hcl
+locals {
+  zones = {
+    "adyxax.eu"            = { emails = "adyxax" }
+    "adyxax.org"           = { emails = "adyxax" }
+    "anne-so-et-julien.fr" = { emails = "no" }
+  }
+}
+
+data "cloudflare_zone" "main" {
+  for_each = local.zones
+
+  name = each.key
+}
+```
+
+### SPF
+
+Then I map each profile to spf records:
+``` hcl
+locals {
+  spf = {
+    "adyxax" = "v=spf1 mx -all"
+    "no"     = "v=spf1 -all"
+  }
+}
+
+resource "cloudflare_record" "spf" {
+  for_each = local.zones
+
+  name    = "@"
+  type    = "TXT"
+  value   = local.spf[each.value.emails]
+  zone_id = data.cloudflare_zone.main[each.key].id
+}
+```
+
+### DMARC
+
+The same mapping system we had for spf can be used here too, but I choose to keep things simple and in the scope of this article. My real setup has some clever tricks to make dmarc notifications work centralized to a single domain that will be the subject another post:
+
+``` hcl
+resource "cloudflare_record" "dmarc" {
+  for_each = { for name, info in local.zones :
+    name => info if info.emails == "no"
+  }
+
+  name    = "@"
+  type    = "TXT"
+  value   = "v=DMARC1;p=reject;sp=reject;pct=100"
+  zone_id = data.cloudflare_zone.main[each.key].id
+}
+```
+
+## Conclusion
+
+Please keep your email DNS records tight and secure!
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