diff --git a/nixos/tests/mailhog.nix b/nixos/tests/mailhog.nix
index ceab93d3b2a8..41d4a97abf3a 100644
--- a/nixos/tests/mailhog.nix
+++ b/nixos/tests/mailhog.nix
@@ -6,11 +6,9 @@
     RTUnreal
   ];
 
-  nodes.machine =
-    { pkgs, ... }:
-    {
-      services.mailhog.enable = true;
-    };
+  nodes.machine = _: {
+    services.mailhog.enable = true;
+  };
 
   testScript = ''
     start_all()
@@ -19,7 +17,7 @@
     machine.wait_for_open_port(1025)
     machine.wait_for_open_port(8025)
     # Test sendmail wrapper (this uses smtp, which tests the connection)
-    machine.succeed('printf "To: root@example.com\r\n\r\nthis is the body of the email" | sendmail -f sender@example.com')
+    machine.succeed('printf "To: root@example.com\r\n\r\nthis is the body of the email" | sendmail -t -i -f sender@example.com')
     res = machine.succeed(
         "curl --fail http://localhost:8025/api/v2/messages"
     )