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
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
- Revoke your email API key immediately — Go to your email service dashboard and delete/rotate the current API key to stop all sending
- Check your email service logs — Look at SendGrid, Mailgun, or your email provider to see how many emails were sent and to whom
- Add rate limiting to forms — Limit how many emails any single user or IP address can trigger per hour
- Set up SPF, DKIM, and DMARC records — These DNS records help prove that only you can send emails from your domain
- Add CAPTCHA to public forms — Prevent bots from abusing any form that triggers email sending
- Check for malicious code on your server — Have a developer scan your server for unauthorized scripts or files
Real developers can help you.
Jaime Orts-Caroff
I'm a Senior Android developer, open to work in various fields
AUXLE
I am a Full Stack Developer experienced in building Websites, Web apps and Cross Platform Mobile Apps for Startups and Companies.
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.
Mehdi Ben Haddou
- Founder of Chessigma (1M+ users) & many small projects
- ex Founding Engineer @Uplane (YC F25)
- ex Software Engineer @Amazon and @Booking.com
Prakash Prajapati
I’m a Senior Python Developer specializing in building secure, scalable, and highly available systems. I work primarily with Python, Django, FastAPI, Docker, PostgreSQL, and modern AI tooling such as PydanticAI, focusing on clean architecture, strong design principles, and reliable DevOps practices. I enjoy solving complex engineering problems and designing systems that are maintainable, resilient, and built to scale.
Pratik
SWE with 15+ years of experience building and maintaining web apps and extensive BE infrastructure
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.
Bastien Labelle
Full stack dev w/ 20+ years of experience
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.
Kingsley Omage
Fullstack software engineer passionate about AI Agents, blockchain, LLMs.
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Get HelpFrequently 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.