diff --git a/packages/email-renderer/package.json b/packages/email-renderer/package.json
index 4d4d5c0a..5c7cca90 100644
--- a/packages/email-renderer/package.json
+++ b/packages/email-renderer/package.json
@@ -1,6 +1,6 @@
 {
   "name": "@wrnexus/email-renderer",
-  "version": "0.1.16",
+  "version": "0.1.17",
   "type": "module",
   "description": "WRNexus block email renderers with HTML, text, AMP Email, and MJML interoperability.",
   "exports": {
diff --git a/packages/email-renderer/src/blocks.ts b/packages/email-renderer/src/blocks.ts
index d6dbe76d..232cbb1b 100644
--- a/packages/email-renderer/src/blocks.ts
+++ b/packages/email-renderer/src/blocks.ts
@@ -158,8 +158,13 @@ export const sectionBlock = defineBlock({
         `<table role="presentation" width="100%" cellpadding="0" cellspacing="0" border="0"><tr><td class="section"><table role="presentation" width="100%" cellpadding="0" cellspacing="0" border="0">${slots.content}</table></td></tr></table>`,
         node,
       ),
-    mjml: ({ node, slots }) =>
-      `<mj-section background-color="${html(attrs(node).background)}" padding="${html(attrs(node).padding)}"><mj-column>${slots.content}</mj-column></mj-section>`,
+    mjml: ({ node, slots }) => {
+      const children = node.slots.content ?? [];
+      const body = children.length === 1 && children[0]?.type === "layout.columns"
+        ? slots.content
+        : `<mj-column>${slots.content}</mj-column>`;
+      return `<mj-section background-color="${html(attrs(node).background)}" padding="${html(attrs(node).padding)}">${body}</mj-section>`;
+    },
   },
   textRenderer: ({ slots }) => `${slots.content}\n`,
 } satisfies BlockDefinition);
diff --git a/packages/email-renderer/test/email.test.ts b/packages/email-renderer/test/email.test.ts
index 96deba54..ddbad1da 100644
--- a/packages/email-renderer/test/email.test.ts
+++ b/packages/email-renderer/test/email.test.ts
@@ -57,6 +57,20 @@ const document: BlockDocument = {
 };
 
 describe("email renderer", () => {
+  test("builder column rows export without nesting mj-column inside mj-column", async () => {
+    for (const count of [1,2,3,4]) {
+      const draft=structuredClone(document);
+      const content=draft.root.slots.content[0]!.slots.content;
+      draft.root.slots.content[0]!.slots.content=[{id:"columns",type:"layout.columns",version:1,props:{},styles:{},slots:{columns:Array.from({length:count},(_,index)=>({id:`column-${index}`,type:"layout.column",version:1,props:{width:`${100/count}%`},styles:{},slots:{content:index===0?content:[]}}))}}];
+      const result=await renderEmail(draft,{mjml:true});
+      expect(result.ok).toBe(true);
+      if(!result.ok)continue;
+      const mjml=result.value.exports!.mjml!;
+      expect(mjml.match(/<mj-column\b/g)).toHaveLength(count);
+      expect(await validateMjml(mjml)).toEqual([]);
+      expect(mjml).toContain("Hello &lt;world&gt;");
+    }
+  });
   test("global brand logo survives HTML, AMP, and strict MJML export", async () => {
     const draft = structuredClone(document);
     draft.root.props.logoUrl = "https://example.com/logo.png";