Move MX record to its own subdomain

cmdeploy/src/cmdeploy/__init__.py

@@ -616,7 +616,12 @@ def deploy_chatmail(config_path: Path, disable_mail: bool) -> None:
     deploy_iroh_relay(config)
 
     # Deploy acmetool to have TLS certificates.
-    tls_domains = [mail_domain, f"mta-sts.{mail_domain}", f"www.{mail_domain}"]
+    tls_domains = [
+        mail_domain,
+        f"mta-sts.{mail_domain}",
+        f"www.{mail_domain}",
+        f"mx.{mail_domain}",
+    ]
     deploy_acmetool(
         domains=tls_domains,
     )

cmdeploy/src/cmdeploy/chatmail.zone.j2

@@ -7,10 +7,11 @@
 {% if AAAA %}
 {{ mail_domain }}.                   AAAA  {{ AAAA }}
 {% endif %}
-{{ mail_domain }}.                   MX 10 {{ mail_domain }}.
+{{ mail_domain }}.                   MX 10 mx.{{ mail_domain }}.
 _mta-sts.{{ mail_domain }}.          TXT "v=STSv1; id={{ sts_id }}"
 mta-sts.{{ mail_domain }}.           CNAME {{ mail_domain }}.
 www.{{ mail_domain }}.               CNAME {{ mail_domain }}.
+mx.{{ mail_domain }}.                CNAME {{ mail_domain }}.
 {{ dkim_entry }}
 
 ;

cmdeploy/src/cmdeploy/nginx/mta-sts.txt.j2

@@ -1,4 +1,4 @@
 version: STSv1
 mode: enforce
-mx: {{ config.domain_name }}
+mx: mx.{{ config.domain_name }}
 max_age: 2419200