[nullmailer] Do not guess mail host

base.yml

@@ -80,6 +80,7 @@
   vars:
     mail_root: root@crans.org
     mail_snmp_server: smtp.adm.crans.org
+    mail_defaulthost: crans.org
   roles:
     - nullmailer
 

roles/nullmailer/tasks/main.yml

@@ -16,3 +16,9 @@
   copy:
     content: "{{ mail_root }}"
     dest: /etc/nullmailer/adminaddr
+
+- name: Set nullmailer defaulthost
+  copy:
+    content: "{{ mail_defaulthost }}"
+    dest: /etc/nullmailer/defaulthost
+