diff --git a/mcp_modules/backlinks/src/email-policy.js b/mcp_modules/backlinks/src/email-policy.js
new file mode 100644
index 0000000..037e4c5
--- /dev/null
+++ b/mcp_modules/backlinks/src/email-policy.js
@@ -0,0 +1,12 @@
+/** A mailbox-specific emergency stop shared with other Profullstack senders. */
+export function assertEmailSenderAllowed(...addresses) {
+  const blocked = new Set(
+    (process.env.EMAIL_QUEUE_BLOCKED_SENDERS || '')
+      .split(',')
+      .map(address => address.trim().toLowerCase())
+      .filter(Boolean)
+  );
+  if (addresses.some(address => typeof address === 'string' && blocked.has(address.trim().toLowerCase()))) {
+    throw new Error('Outbound sending from this mailbox is paused for administrator review.');
+  }
+}
diff --git a/mcp_modules/backlinks/src/service.js b/mcp_modules/backlinks/src/service.js
index 8704994..3720503 100644
--- a/mcp_modules/backlinks/src/service.js
+++ b/mcp_modules/backlinks/src/service.js
@@ -8,6 +8,7 @@ import puppeteer from 'puppeteer';
 import nodemailer from 'nodemailer';
 import { v4 as uuidv4 } from 'uuid';
 import { backlinksDb } from './database.js';
+import { assertEmailSenderAllowed } from './email-policy.js';
 import {
   validateSubmissionData,
   generateSubmissionContent,
@@ -655,6 +656,7 @@ export class BacklinksService {
    * @returns {Promise<Object>} Email result
    */
   async sendMailgunEmail(submission, campaign, emailConfig) {
+    assertEmailSenderAllowed(emailConfig.from_email || `noreply@${emailConfig.mailgun_domain}`);
     const formData = new FormData();
     formData.append(
       'from',
@@ -706,6 +708,7 @@ export class BacklinksService {
    * @returns {Promise<Object>} Email result
    */
   async sendSmtpEmail(submission, campaign, emailConfig) {
+    assertEmailSenderAllowed(emailConfig.smtp_user, emailConfig.from_email);
     const transporter = nodemailer.createTransporter({
       host: emailConfig.smtp_host,
       port: emailConfig.smtp_port || 587,
diff --git a/mcp_modules/backlinks/test/sending.test.js b/mcp_modules/backlinks/test/sending.test.js
new file mode 100644
index 0000000..44e2658
--- /dev/null
+++ b/mcp_modules/backlinks/test/sending.test.js
@@ -0,0 +1,16 @@
+import assert from 'node:assert/strict';
+import test from 'node:test';
+import { assertEmailSenderAllowed } from '../src/email-policy.js';
+
+test('blocks a configured mailbox before SMTP or Mailgun is called', () => {
+  const previous = process.env.EMAIL_QUEUE_BLOCKED_SENDERS;
+  process.env.EMAIL_QUEUE_BLOCKED_SENDERS = 'other@gmail.com, ettinger@gmail.com';
+  try {
+    assert.throws(() => assertEmailSenderAllowed('ettinger@gmail.com'), /paused for administrator review/);
+    assert.throws(() => assertEmailSenderAllowed('ETTINGER@gmail.com'));
+    assert.doesNotThrow(() => assertEmailSenderAllowed('business@example.com'));
+  } finally {
+    if (previous === undefined) delete process.env.EMAIL_QUEUE_BLOCKED_SENDERS;
+    else process.env.EMAIL_QUEUE_BLOCKED_SENDERS = previous;
+  }
+});
diff --git a/package.json b/package.json
index 641864b..8cba4dc 100644
--- a/package.json
+++ b/package.json
@@ -55,7 +55,7 @@
     "puppeteer-extra": "^3.3.6",
     "puppeteer-extra-plugin-stealth": "^2.11.2",
     "stream-transform": "^3.5.1",
-    "zod": "4.6.5"
+    "zod": "4.6.7"
   },
   "devDependencies": {
     "chai": "^4.5.0",