Hi, I’m Scott, an IT professional with over 20 years of experience in IT infrastructure, systems design, and cloud technologies. Over my career, I’ve specialised in email architecture, designing and supporting complex mail systems for organisations of all sizes. Today, I work in the cybersecurity industry, helping companies secure their communications and protect their people, data, and brands.
Email is one of the most critical communication channels for any organisation, but it’s also one of the most targeted by cyber threats. SPF (Sender Policy Framework) is a fundamental technology that helps prevent email spoofing and phishing attacks. Unfortunately, the SPF standard has a strict 10 DNS lookup limit. When this limit is exceeded, domains encounter the dreaded SPF PermError, leading to failed DMARC checks, rejected emails, and serious deliverability issues.
Over the years, I’ve seen countless email administrators struggle with this exact problem. It was frustrating to watch teams waste hours troubleshooting broken SPF records or manually flattening includes just to stay compliant. I knew there had to be a smarter way to solve this problem — one that could scale without adding unnecessary complexity.
In 2022, I launched my first open-source project, Expurgate, a self-hosted, Dockerized SPF macro hosting solution designed for mail administrators who wanted to host their own SPF macro infrastructure.
Shortly after, I released Expurgate Solo, a simplified, single-container version of the project, available on GitHub. These projects gave administrators full control over their SPF macro hosting while providing a scalable, open-source toolset.
However, as the user base grew, I started receiving frequent requests: “Can Expurgate be made available as a cloud-hosted service?”
Expurgate was originally built on rbldnsd, which relies heavily on static configuration files.
To run it as a cloud service, it would require complex user signups, logins, and periodic generation of config files — not ideal for a lightweight, highly-available service.
This challenge inspired me to completely re-think the solution. I decided to design a new version of SPF macro hosting, one built specifically for the cloud and capable of handling global traffic efficiently.
After careful consideration, I chose to host SPF Guru using Bunny.net’s Magic Container environment. This platform allows me to run SPF Guru in secure, containerized environments that are automatically deployed at the edge of the internet — close to end users.
By leveraging anycast routing, SPF Guru can instantly scale up or down based on demand. Whether 10 people or 10,000 people are performing lookups, the service remains fast, reliable, and cost-efficient. This edge-hosted architecture also helps minimise latency and improve DNS resolution performance worldwide.
Running SPF Guru on Bunny.net isn’t free. I personally cover the hosting costs because I believe in providing a reliable, accessible service for the email community. While I can’t promise the solution will remain free forever, my goal is to run and maintain SPF Guru at least until 2030, depending on demand and usage levels.
SPF Guru is a labour of love — a way for me to give back to the IT and email admin communities that I’ve been part of for two decades. If you find value in the service and want to help keep it running, donations are always appreciated: buymeacoffee.com/smc83. Or host your project on bunny.net using my referal code https://bunny.net?ref=ndyy4946y2
SPF Guru is more than just a tool. It’s about making life easier for email administrators who are tasked with protecting their organisations from spoofing and phishing attacks. By providing a free, easy-to-use SPF hosting solution, I hope to reduce the number of failed DMARC checks, prevent legitimate emails from being rejected, and ultimately make email communication safer and more reliable for everyone.
As SPF Guru grows, I plan to add new features, expand the network, and continue optimising performance. The email security landscape is constantly evolving, and I’m committed to ensuring SPF Guru evolves with it.
Thank you for taking the time to learn about this project. Whether you’re here to fix an SPF PermError, improve your DMARC compliance, or simply explore new technologies, I’m glad you’ve found SPF Guru — and I look forward to supporting you on your email security journey.
- Scott
Creator of SPF Guru