/etc/mailname must be set for nullmailer to work properly.

README.md

@@ -20,6 +20,9 @@ [email protected] via SMTP to smtp.example.com
 This may require you to configure your SMTP server to accept
 incoming email from various machines.
 
+NOTE: /etc/mailname must be set to a reasonable value. This
+module will, by default, set it to $::fqdn
+
 Basic usage
 -----------
 

manifests/config.pp

@@ -1,4 +1,15 @@
 class nullmailer::config {
+
+  if $nullmailer::manage_etc_mailname == true {
+
+    file {'nullmailer /etc/mailname for $fqdn':
+      name => '/etc/mailname',
+      content => "$::fqdn\n",
+      ensure  => present,
+    }
+
+  }
+
   file { '/etc/nullmailer/remotes':
     content => "$nullmailer::remoterelay smtp\n",
     require => Class['nullmailer::package'],

manifests/init.pp

@@ -2,6 +2,7 @@
   $package = $nullmailer::params::package,
   $absentpackages = $nullmailer::params::absentpackages,
   $service = $nullmailer::params::service,
+  $manage_etc_mailname = $nullmailer::params::manage_etc_mailname,
   $adminaddr = "root@$::domain",
   $remoterelay = "smtp.$::domain",
 

manifests/params.pp

@@ -7,6 +7,7 @@
                          'courier-mta', 'lsb-invalid-mta',
                          'exim4-base', 'exim4-config', 'exim4']
       $service = 'nullmailer'
+      $manage_etc_mailname = true
     }
     default: {
       fail("Unsupported platform: ${::operatingsystem}")