diff --git a/tests/extern.nix b/tests/extern.nix
index 63711aa..523f6ae 100644
--- a/tests/extern.nix
+++ b/tests/extern.nix
@@ -152,10 +152,14 @@ import <nixpkgs/nixos/tests/make-test.nix> {
 
       subtest "remove sensitive information on submission port", sub {
         $client->succeed("cat ~/mail/* >&2");
-        # make sure our IP is _not_ in the email header
+        ## make sure our IP is _not_ in the email header
         $client->fail("grep `ip addr | grep 'state UP' -A2 | tail -n1 | awk '{print \$2}' | cut -f1  -d'/'` ~/mail/*");
       };
 
+      subtest "have correct fqdn as sender", sub {
+        $client->succeed("grep 'Received: from mail.example.com' ~/mail/*");
+      };
+
       subtest "dkim singing, multiple domains", sub {
           $client->succeed("rm ~/mail/*");
           $client->succeed("rm mail.txt");