Cursor email

Email Queue Backing Up and Delays in Cursor Application

Your Cursor-built application's email delivery is severely delayed. Verification emails arrive 30 minutes late, password reset links expire before the email is delivered, and notification emails pile up in a queue that processes too slowly or gets stuck entirely.

Cursor often generates email sending code that runs synchronously in the request handler, blocking the HTTP response while waiting for SMTP. As your app grows, this approach fails because each email takes 1-3 seconds to send, overwhelming your server during traffic spikes. Alternatively, Cursor may set up a queue but configure it incorrectly, causing emails to accumulate without being processed.

Users complain about not receiving emails, repeatedly click "resend", creating even more queue pressure, and eventually abandon your app because they can't complete basic flows like email verification or password reset.

Error Messages You Might See

Error: Too many requests - rate limit exceeded Error: Queue connection refused (Redis unavailable) Timeout: Email sending exceeded 30s timeout Error: Job stalled and will be retried Warning: Queue depth exceeds 1000 pending messages
Error: Too many requests - rate limit exceededError: Queue connection refused (Redis unavailable)Timeout: Email sending exceeded 30s timeoutError: Job stalled and will be retriedWarning: Queue depth exceeds 1000 pending messages

Common Causes

  • Synchronous email sending in request handlers — Each API request waits for the email to send before responding, creating a bottleneck under load
  • Email provider rate limits hit — SendGrid, Resend, and other providers have per-second and per-day sending limits that your queue exceeds
  • Queue worker not running in production — The background job processor (Bull, BullMQ, Celery) wasn't started or configured in the production deployment
  • Dead letter queue filling up — Failed emails retry indefinitely or get sent to a dead letter queue without alerting
  • No concurrency limit on queue workers — Too many concurrent send operations overwhelm the SMTP connection or hit API rate limits
  • Memory leak in queue processor — The worker process slowly consumes more memory until it's killed by the OS, halting all processing

How to Fix It

  1. Send emails asynchronously — Never send emails in the HTTP request handler. Use a background job queue (BullMQ with Redis, or a serverless queue like AWS SQS) to process emails separately
  2. Respect provider rate limits — Configure your queue worker's concurrency to stay under your email provider's rate limits. SendGrid allows 600 requests per minute on free tier
  3. Verify queue workers are running — Check your production deployment includes the worker process. For Docker, ensure the worker is a separate service. For PaaS, configure a worker dyno/process
  4. Add retry logic with exponential backoff — Configure failed emails to retry with increasing delays (1s, 5s, 30s, 5min) instead of immediately retrying or giving up
  5. Monitor queue depth and processing rate — Add metrics for queue size, processing time, and failure rate. Alert when the queue depth exceeds a threshold or processing stops
  6. Prioritize transactional emails — Use separate queues for critical emails (verification, password reset) and non-critical ones (marketing, notifications). Process critical emails first

Real developers can help you.

Richard McSorley Richard McSorley Full-Stack Software Engineer with 8+ years building high-performance applications for enterprise clients. Shipped production systems at Walmart (4,000+ stores), Cigna (20M+ users), and Arkansas Blue Cross. 5 patents in retail/supply chain tech. Currently focused on AI integrations, automation tools, and TypeScript-first architectures. Matthew Jordan Matthew Jordan I've been working at a large software company named Kainos for 2 years, and mainly specialise in Platform Engineering. I regularly enjoy working on software products outside of work, and I'm a huge fan of game development using Unity. I personally enjoy Python & C# in my spare time, but I also specialise in multiple different platform-related technologies from my day job. Jen Jacobsen Jen Jacobsen I’m a Full-Stack Developer with over 10 years of experience building modern web and mobile applications. I enjoy working across the full product lifecycle — turning ideas into real, well-built products that are intuitive for users and scalable for businesses. I particularly enjoy building mobile apps, modern web platforms, and solving complex technical problems in a way that keeps systems clean, reliable, and easy to maintain. Daniel Vázquez Daniel Vázquez Software Engineer with over 10 years of experience on Startups, Government, big tech industry & consulting. rayush33 rayush33 JavaScript (React.js, React Native, Node.js) Developer with demonstrated industry experience of 4+ years, actively looking for opportunities to hone my skills as well as help small-scale business owners with solutions to technical problems MFox MFox Full-stack professional senior engineer (15+years). Extensive experience in software development, qa, and IP networking. zipking zipking I am a technologist and product builder dedicated to creating high-impact solutions at the intersection of AI and specialized markets. Currently, I am focused on PropScan (EstateGuard), an AI-driven SaaS platform tailored for the Japanese real estate industry, and exploring the potential of Archify. As an INFJ-T, I approach development with a "systems-thinking" mindset—balancing technical precision with a deep understanding of user needs. I particularly enjoy the challenge of architecting Vertical AI SaaS and optimizing Small Language Models (SLMs) to solve specific, real-world business problems. Whether I'm in a CTO-level leadership role or hands-on with the code, I thrive on building tools that turn complex data into actionable value. Jared Hasson Jared Hasson Full time lead founding dev at a cyber security saas startup, with 10 yoe and a bachelor's in CS. Building & debugging software products is what I've spent my time on for forever Sage Fulcher Sage Fulcher Hey I'm Sage! Im a Boston area software engineer who grew up in South Florida. Ive worked at a ton of cool places like a telehealth kidney care startup that took part in a billion dollar merger (Cricket health/Interwell health), a boutique design agency where I got to work on a ton of exciting startups including a photography education app, a collegiate Esports league and more (Philosophie), a data analytics as a service startup in Cambridge (MA) as well as at Phillips and MIT Lincoln Lab where I designed and developed novel network security visualizations and analytics. I've been writing code and furiously devoted to using computers to make people’s lives easier for about 17 years. My degree is in making computers make pretty lights and sounds. Outside of work I love hip hop, the Celtics, professional wrestling, magic the gathering, photography, drumming, and guitars (both making and playing them) Jaime Orts-Caroff Jaime Orts-Caroff I'm a Senior Android developer, currently working at Aircall. I'm open to work in various fields!

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Frequently Asked Questions

How do I send emails without slowing down my API?

Use a background job queue. Add the email to a queue (BullMQ, SQS, or even a database table) in your API handler, then return immediately. A separate worker process picks up queued emails and sends them asynchronously.

What email sending rate should I target?

Start conservative: 1-2 emails per second. Check your provider's limits (SendGrid free: 100/day, paid: 600/min; Resend free: 100/day; AWS SES: varies by region). Scale up gradually and monitor for bounces and rate limit errors.

Related Cursor Issues

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