diff --git a/nixos/modules/services/mail/public-inbox.nix b/nixos/modules/services/mail/public-inbox.nix
index ab7ff5f726a4..9cd6726e6cb2 100644
--- a/nixos/modules/services/mail/public-inbox.nix
+++ b/nixos/modules/services/mail/public-inbox.nix
@@ -275,7 +275,11 @@ in
           default = {};
           description = lib.mdDoc "public inboxes";
           type = types.submodule {
-            freeformType = with types; /*inbox name*/attrsOf (/*inbox option name*/attrsOf /*inbox option value*/iniAtom);
+            # Keeping in line with the tradition of unnecessarily specific types, allow users to set
+            # freeform settings either globally under the `publicinbox` section, or for specific
+            # inboxes through additional nesting.
+            freeformType = with types; attrsOf (oneOf [ iniAtom (attrsOf iniAtom) ]);
+
             options.css = mkOption {
               type = with types; listOf str;
               default = [];