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/ Dor Yaloz Dor Yaloz SW engineer with 6+ years of experience, I worked with React/Node/Python did projects with React+Capacitor.js for ios Supabase expert 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. Antriksh Narang Antriksh Narang 5 years+ Experienced Dev (Specially in Web Development), can help in python, javascript, react, next.js and full stack web dev technologies. Milan Surelia Milan Surelia Milan Surelia is a Mobile App Developer with 5+ years of experience crafting scalable, cross-platform apps at 7Span and Meticha. At 7Span, he engineers feature-rich Flutter apps with smooth performance and modern UI. As the Co-Founder of Meticha, he builds open-source tools and developer-focused products that solve real-world problems. Expertise: 💡 Developing cross-platform apps using Flutter, Dart, and Jetpack Compose for Android, iOS, and Web. 🖋️ Sharing insights through technical writing, blogging, and open-source contributions. 🤝 Collaborating closely with designers, PMs, and developers to build seamless mobile experiences. Notable Achievements: 🎯 Revamped the Vepaar app into Vepaar Store & CRM with a 2x performance boost and smoother UX. 🚀 Launched Compose101 — a Jetpack Compose starter kit to speed up Android development. 🌟 Open source contributions on Github & StackOverflow for Flutter & Dart 🎖️ Worked on improving app performance and user experience with smart solutions. Milan is always happy to connect, work on new ideas, and explore the latest in technology. Caio Rodrigues Caio Rodrigues I'm a full-stack developer focused on building practical and scalable web applications. My main experience is with **React, TypeScript, and modern frontend architectures**, where I prioritize clean code, component reusability, and maintainable project structures. I have strong experience working with **dynamic forms, state management (Redux / React Hook Form), and complex data-driven interfaces**. I enjoy solving real-world problems by turning ideas into reliable software that companies can actually use in their daily operations. Beyond coding, I care about **software quality and architecture**, following best practices for componentization, code organization, and performance optimization. I'm also comfortable working across the stack when needed, integrating APIs, handling business logic, and helping transform prototypes into production-ready systems. My goal is always to deliver solutions that are **simple, efficient, and genuinely useful for the people using them.** Stanislav Prigodich Stanislav Prigodich 15+ years building iOS and web apps at startups and enterprise companies. I want to use that experience to help builders ship real products - when something breaks, I'm here to fix it. hanson1014 hanson1014 Full-stack developer experienced in fixing and deploying AI-generated apps from Lovable, Bolt.new, Cursor, and Replit. I specialize in debugging Supabase integration issues (auth flows, RLS policies, database connections), fixing broken deployments, resolving routing/blank screen problems, and cleaning up messy React/Vite codebases. I also build production apps with the Claude API and have shipped a Mac desktop dev tool (Nexterm from scratch. Based in Hong Kong, fast turnaround. Jacek Rozanski Jacek Rozanski Senior PHP/Symfony developer and DevOps engineer with 20+ years of professional experience, running opcode.pl (web development agency, est. 2004). Day job: I'm the sole backend developer at merketing company where I own and maintain 11 PHP/Symfony microservices on AWS (ECS Fargate, RDS, S3, CloudFront), handle the full CI/CD pipeline (Bitbucket Pipelines, Docker), and manage monitoring with Sentry and CloudWatch. These services handle high request volumes in production every month. What I bring to AI-built apps: - I audit and fix security issues (OWASP methodology), performance bottlenecks, and architectural problems in codebases generated by Cursor, Claude Code, Lovable, Bolt, and v0 - I refactor AI-generated prototypes into production-grade applications with proper error handling, testing, and clean architecture (SOLID, DDD, hexagonal architecture) - I set up the infrastructure AI tools don't touch: AWS hosting, CI/CD pipelines, automated deployments, database optimization, monitoring, and alerting - I integrate external services: payment providers, email systems, partner APIs, SSO/auth Tech stack: PHP 8.x, Symfony, React, Next.js, PostgreSQL, MySQL, Docker, AWS (ECS, RDS, S3, SQS/SNS, CloudFront), Terraform, Supabase. I also use AI tools daily (Claude Code, Cursor) in my own workflow, so I understand both the strengths and the gaps in AI-generated code. Based in Poland (CET timezone). Available for async work and calls during EU/US business hours.

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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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