diff --git a/modules/services/mail/postfix.nix b/modules/services/mail/postfix.nix
index 3eda558f1c5..3a28e81eb15 100644
--- a/modules/services/mail/postfix.nix
+++ b/modules/services/mail/postfix.nix
@@ -81,8 +81,8 @@ let
       smtpd_use_tls = yes 
 
       recipientDelimiter = ${cfg.recipientDelimiter}
-
-    '';
+    ''
+    + cfg.extraConfig;
 
   aliases = 
     optionalString (cfg.postmasterAlias != "") ''
@@ -227,6 +227,13 @@ in
         ";
       };
 
+      extraConfig = mkOption {
+        default = "";
+        description = "
+          Extra configuration, will be added verbatim to the configuration file.
+        ";
+      };
+
       sslCert = mkOption {
         default = "";
         description = "SSL certificate to use.";