Common Issues security

My App Is Sending Spam Emails I Didn't Create

Users are telling you they're getting weird emails from your app — promotional messages, phishing attempts, or password reset links they didn't request. You didn't set up any of these emails, and you have no idea how they're being sent.

This usually means someone has gained access to your email sending service (like SendGrid, Mailgun, or your SMTP credentials) and is using your account to blast out spam. Your domain and reputation are being destroyed with every email sent.

The damage goes beyond annoying your users. Email providers like Gmail and Outlook may permanently blacklist your domain, meaning even your legitimate emails will go to spam forever if you don't act quickly.

Error Messages You Might See

Bounce notification: message rejected Email delivery failed: blacklisted Your sending has been suspended SPF check failed Users reporting phishing from your domain
Bounce notification: message rejectedEmail delivery failed: blacklistedYour sending has been suspendedSPF check failedUsers reporting phishing from your domain

Common Causes

  • Email API key stolen — Your SendGrid, Mailgun, or other email service API key is exposed in your code or has been stolen
  • Contact form exploited — Your app's contact form or email feature has no rate limiting, so bots are using it to send thousands of messages
  • Open email relay — Your email server is configured to let anyone send emails through it without authentication
  • Compromised server — Someone gained access to your server and installed their own email-sending scripts
  • Spoofed sender address — Someone is sending emails that look like they're from your domain (you can't fully prevent this without proper DNS records)

How to Fix It

  1. Revoke your email API key immediately — Go to your email service dashboard and delete/rotate the current API key to stop all sending
  2. Check your email service logs — Look at SendGrid, Mailgun, or your email provider to see how many emails were sent and to whom
  3. Add rate limiting to forms — Limit how many emails any single user or IP address can trigger per hour
  4. Set up SPF, DKIM, and DMARC records — These DNS records help prove that only you can send emails from your domain
  5. Add CAPTCHA to public forms — Prevent bots from abusing any form that triggers email sending
  6. Check for malicious code on your server — Have a developer scan your server for unauthorized scripts or files

Real developers can help you.

Rudra Bhikadiya Rudra Bhikadiya I build and fix web apps across Next.js, Node.js, and DBs. Comfortable jumping into messy code, broken APIs, and mysterious bugs. If your project works in theory but not in reality, I help close that gap. Vlad Temian Vlad Temian 15+ years shipping production infrastructure for startups. Former CTO at qed.builders (acquired by The Sandbox). Cursor ambassador and agentic tooling builder. I've scaled systems, automated deployments, and built observability tools for AI coding workflows. I specialize in taking vibe-coded apps from broken prototype to production-ready: fixing Supabase auth/RLS, Stripe integrations, deployment pipelines, and cleaning up AI-generated spaghetti. I build tools in this space (agentprobe, claudebin, micode) and understand both sides: how AI generates code and why it breaks. https://blog.vtemian.com/ BurnHavoc BurnHavoc Been around fixing other peoples code for 20 years. ISHANTDEEP SINGH ISHANTDEEP SINGH Senior Software Engineer with 7+ years of experience in React, JavaScript, TypeScript, Next.js, and Node.js. I’ve also worked as a tech lead for startups, owning end-to-end technical execution including architecture, development, scaling, and delivery. I bring a strong mix of hands-on coding, product thinking, and technical leadership, and I’m comfortable building products from scratch as well as improving and scaling existing systems. prajwalfullstack prajwalfullstack Hi Im a full stack developer, a vibe coded MVP to Market ready product, I'm here to help Meïr Ankri Meïr Ankri Full-stack developer specializing in React / Next.js / Node.js with 6+ years of experience. I've worked across various sectors including automotive (Reezocar/Société Générale), healthcare (Medical Link SaaS), and e-commerce (Glasman). I build web apps end-to-end, from architecture to production, with a focus on scalability, performance, and code quality. I also mentor junior developers and contribute to technical decisions and code reviews. Franck Plazanet Franck Plazanet I am a Strategic Engineering Leader with over 8 years of experience building high-availability enterprise systems and scaling high-performing technical teams. My focus is on bridging the gap between complex technology and business growth. Core Expertise: 🚀 Leadership: Managing and coaching teams of 15+ engineers, fostering a culture of accountability and continuous improvement. 🏗️ Architecture: Enterprise Core Systems, Multi-system Integration (ERP/API/ETL), and Core Database Structure. ☁️ Cloud & Scale: AWS Expert; architected systems handling 10B+ monthly requests and managing 100k+ SKUs. 📈 Business Impact: Aligning tech strategy with P&L goals to drive $70k+ in monthly recurring revenue. I thrive on "out-of-the-box" thinking to solve complex technical bottlenecks and am always looking for ways to use automation to improve business productivity. Simon A. Simon A. I'm a backend developer building APIs, emulators, and interactive game systems. Professionally, I've developed Java/Spring reporting solutions, managed relational and NoSQL databases, and implemented CI/CD workflows. legrab legrab I'll fill this later Kingsley Omage Kingsley Omage Fullstack software engineer passionate about AI Agents, blockchain, LLMs.

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Frequently Asked Questions

How do I know if my domain has been blacklisted?

Use free tools like MXToolbox.com or mail-tester.com to check if your domain or IP is on any email blacklists. If it is, you'll need to clean up the issue and then request removal from each blacklist.

Can I stop people from sending emails that look like they're from my domain?

You can make it much harder by setting up SPF, DKIM, and DMARC records in your domain's DNS settings. These tell email providers which servers are authorized to send email on your behalf.

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