Cold Email Engineer – Tech Co-Founder - LLM Personalization & Sending Infrastructure

Deal Baker; United Kingdom; Remote; GBP 50,000 - 80,000; Full time

Job summary

A leading startup is seeking a Cold Email Engineer to architect and scale their LLM-powered personalization engine. This role offers significant equity and the chance to make an immediate impact by driving revenue through personalized outreach. Ideal candidates will have deep technical expertise in cold-email infrastructure and a passion for building innovative solutions.

Benefits

Significant equity stake

Revenue sharing from products built

Path to transition into traditional salary + equity

Remote-first culture

Technical freedom to choose stack and architecture

Qualifications

• Battle-tested knowledge of cold-email infrastructure.
• Hands-on experience building large-scale email sending systems.
• Expert-level understanding of spam filters and compliance requirements.

Responsibilities

• Design and implement LLM-powered personalization pipelines.
• Build infrastructure for high-volume personalized email content.
• Lead technical decisions for a revenue-generating product.

Skills

SMTP optimization

Queuing systems

Deliverability monitoring

Prompt engineering

Problem-solving

Job description

Cold Email Engineer – Tech Co-Founder - LLM Personalization & Sending Infrastructure

Cold Email Engineer – Tech Co-Founder - LLM Personalization & Sending Infrastructure

1 day ago Be among the first 25 applicants

Transform Intent Data Into Revenue-Driving, Hyper-Personalized Outreach

SignalsAPI.com is a bootstrapped, profitable startup that's mastered intent detection. Now we're launching our most ambitious product yet: an LLM-powered personalization engine that transforms raw intent signals into ultra-timely, hyper-personalized cold emails that feel like one-off conversations.

We're not just hiring an engineer—we're seeking a technical co-founder who will architect, build, and scale the personalization layer that turns our existing customer base into a growth engine.

Why This Role Matters

• Perfect Timing Meets Perfect Messaging: We've cracked intent detection. Now we need someone who can deliver the perfect message at the exact moment prospects are ready to buy.
• Real Revenue, Real Impact: This isn't a "maybe someday" product. We're rolling this out to paying customers who are already seeing results from our intent data. Your work will directly drive revenue from day one.
• Bootstrapped & Battle-Tested: No VC pressure, no artificial timelines. We're profitable, growing sustainably, and building for the long term with real customer validation.

Your Mission As Co-Founder

Architect the Future of Personalized Outreach

• Design and implement LLM-powered personalization pipelines that fuse massive intent datasets with real-time, context-aware messaging
• Transform high-volume signals into ultra-personalized email content using advanced prompt engineering techniques
• Build the infrastructure that makes every message feel like a human wrote it specifically for that prospect
• Architect robust SMTP infrastructure with intelligent queuing, domain warm-up protocols, and deliverability optimization
• Implement comprehensive bounce handling, spam filter navigation, and sender reputation management
• Build monitoring dashboards and error handling systems that ensure 99.9%+ reliability
• Ensure full compliance with unsubscribe requirements and GDPR regulations

Own the Technical Vision

• Lead technical decisions for a revenue-generating product serving enterprise customers
• Build scalable distributed systems that handle millions of personalized messages
• Implement real-time data processing pipelines that turn intent signals into actionable outreach
• Drive rapid iteration cycles based on customer feedback and performance metrics

What You Bring to the Partnership

Deep Technical Expertise

• Battle-tested knowledge of cold-email infrastructure: SMTP optimization, queuing systems, deliverability monitoring, warm-up strategies
• Hands-on experience building large-scale email sending systems that consistently hit inboxes
• Expert-level understanding of spam filters, sender reputation, bounce handling, and compliance requirements
• Proven experience with LLMs (OpenAI, Hugging Face) and advanced prompt engineering
• Customer obsession: You understand that great technology serves real customer needs
• Problem-solving instinct: You see challenges as opportunities to create competitive advantages

What This Partnership Offers

True Co-Founder Equity

• Significant equity stake with real upside as we scale
• Revenue sharing from the products you build
• Path to transition into traditional salary + equity after 2-3 months if preferred

Immediate Impact & Ownership

• Own the entire personalization and email infrastructure stack
• Direct access to existing customer base for immediate product validation
• Your code will be generating revenue within weeks, not months
• Remote-first culture with flexibility to work where you're most productive
• Fast-paced execution: From concept to customer deployment in weeks
• Customer-driven development: Regular interaction with users to validate and iterate
• Technical freedom: Choose your stack, architecture, and deployment strategies

Growth Trajectory

• Built-in demand from existing SignalsAPI customer base
• Clear path to scale as we win new enterprise clients
• Opportunity to expand into adjacent personalization products
• Foundation for building a category-defining company in sales automation

The Ideal Candidate

You're not just looking for another engineering role—you want to build something that matters. You've seen the power of LLMs for personalization, but you also understand that great AI products require bulletproof infrastructure. You know that the difference between a demo and a business is reliability, compliance, and scale.

You've built cold-email systems before and learned the hard lessons about deliverability. You understand that sending millions of emails isn't just about technical throughput—it's about reputation management, compliance, and creating genuine value for recipients.

Most importantly, you're excited about the opportunity to take proven intent data technology and layer on cutting-edge personalization to create something that transforms how B2B companies approach outreach.

Next Steps

Ready to architect the future of personalized outreach? We're moving fast and looking for someone who can start making an impact immediately.

Send us:

• A brief note about why this opportunity excites you
• Examples of LLM personalization or cold-email infrastructure you've built
• Your thoughts on how you'd approach building this system at scale

Email: [e-mail]

Subject Line: "Cold Email Engineer"

We review applications daily and will get back to qualified candidates within 48 hours.

Seniority level

• Seniority level

  Mid-Senior level

Employment type

• Employment type

  Contract

Job function

• Job function

  Information Technology

• Industries

  Software Development

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