diff --git a/nixos/tests/alps.nix b/nixos/tests/alps.nix
index fd4ee51e6e20..0ea9ea46e5ac 100644
--- a/nixos/tests/alps.nix
+++ b/nixos/tests/alps.nix
@@ -28,8 +28,10 @@ in
         enableSubmission = true;
         enableSubmissions = true;
         tlsTrustedAuthorities = "${certs.ca.cert}";
-        sslCert = "${certs.${domain}.cert}";
-        sslKey = "${certs.${domain}.key}";
+        config.smtpd_tls_chain_files = [
+          "${certs.${domain}.key}"
+          "${certs.${domain}.cert}"
+        ];
       };
       services.dovecot2 = {
         enable = true;
diff --git a/nixos/tests/schleuder.nix b/nixos/tests/schleuder.nix
index 05e22de056bd..2dab607cbd2f 100644
--- a/nixos/tests/schleuder.nix
+++ b/nixos/tests/schleuder.nix
@@ -12,8 +12,10 @@ import ./make-test-python.nix {
         enable = true;
         enableSubmission = true;
         tlsTrustedAuthorities = "${certs.ca.cert}";
-        sslCert = "${certs.${domain}.cert}";
-        sslKey = "${certs.${domain}.key}";
+        config.smtpd_tls_chain_files = [
+          "${certs.${domain}.key}"
+          "${certs.${domain}.cert}"
+        ];
         inherit domain;
         destination = [ domain ];
         localRecipients = [