diff --git a/nixos/modules/services/mail/mlmmj.nix b/nixos/modules/services/mail/mlmmj.nix
index 1545c60f4de..db3a266d011 100644
--- a/nixos/modules/services/mail/mlmmj.nix
+++ b/nixos/modules/services/mail/mlmmj.nix
@@ -88,6 +88,7 @@ in
 
     services.postfix = {
       enable = true;
+      recipientDelimiter= "+";
       extraMasterConf = ''
         mlmmj unix - n n - - pipe flags=ORhu user=mlmmj argv=${pkgs.mlmmj}/bin/mlmmj-receive -F -L ${spoolDir}/$nextHop
       '';
diff --git a/nixos/modules/services/mail/postfix.nix b/nixos/modules/services/mail/postfix.nix
index 3d9bb9ccf24..29e0cf7a882 100644
--- a/nixos/modules/services/mail/postfix.nix
+++ b/nixos/modules/services/mail/postfix.nix
@@ -77,6 +77,8 @@ let
       smtpd_tls_key_file = ${cfg.sslKey}
 
       smtpd_use_tls = yes
+
+      recipient_delimiter = ${cfg.recipientDelimiter}
     ''
     + optionalString (cfg.virtual != "") ''
       virtual_alias_maps = hash:/etc/postfix/virtual
@@ -289,6 +291,14 @@ in
         description = "SSL key to use.";
       };
 
+      recipientDelimiter = mkOption {
+        default = "";
+        example = "+";
+        description = "
+          Delimiter for address extension: so mail to user+test can be handled by ~user/.forward+test
+        ";
+      };
+
       virtual = mkOption {
         default = "";
         description = "