How We Actually Doubled Our Cold Email Deliverability (The Techniques We Used)
Troy Aitken breaks down the exact domain, ESP, and inbox-placement techniques BuzzLead used to 2x cold email deliverability in practice.
Deliverability isn't a problem you solve once. It's a moving target, and if you're treating it like a checkbox, you're going to keep bleeding sends to spam. We had to work through a series of real failures before we found the combination that doubled our inbox placement rates. Here's exactly what we changed and why.
We Stopped Assuming One Domain Provider Was Good Enough
The first thing we did was switch domain providers. This sounds minor until you realize that where you register a domain affects its baseline reputation, how it ages, and how ESP filters interpret it. We landed on Porkbun as our primary registrar. It's not glamorous, but it works. The domains are cheap, the setup is straightforward, and we've had consistent results at scale.
At BuzzLead we manage 32,000+ sending accounts, so even a marginal edge at the domain-provider level compounds fast. If you're running any meaningful volume and you haven't tested your registrar as a variable, test it.
We also worked with reseller accounts during this process. That opened up more flexibility in how we structured sending infrastructure and gave us options that a standard retail account wouldn't.
We Stopped Relying on a Single ESP
One of the most concrete changes we made was building a mixed infrastructure of Microsoft and Google accounts. Not one or the other. Both.
The reason is simple: ESP optimization opportunities exist on both sides, and they shift. What's landing in the inbox on Google today might not be landing there next quarter. Having both in your sending stack means you can lean into whichever is performing better at any given time, rather than being hostage to one provider's algorithm.
This isn't about spreading sends randomly. It's about having actual options when one environment tightens up. If you're all-in on Google Workspace and Gmail starts hammering cold email harder, you have nowhere to go. Microsoft gives you a path.
We Started Parking Our IP and Testing at Scale
The piece that probably moved the needle most was parking our IP address and then running deliverability checks at scale using tools like EmailGuard.
Parking your IP is about controlling what that IP is associated with before it ever touches a live send. You're not just hoping for a clean reputation. You're actively building one before it matters.
EmailGuard gave us two things. First, the ability to park the IP in a way that established its reputation deliberately. Second, live visibility into whether our mail was landing in the inbox across Microsoft Outlook and SMTP providers. That second part is critical. You can't fix what you're not measuring, and guessing at placement is how you run a campaign into the ground without knowing it until the numbers come back broken.
Running these checks at scale is different from running a one-off test before a campaign. We're talking about continuous monitoring. Deliverability isn't a pre-flight checklist. It's an ongoing signal you have to watch.
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The Real Lesson: Treat It as a Learning Curve, Not a Finish Line
What changed most for us wasn't any single tactic. It was the mindset around the problem. We stopped looking for a permanent fix and started treating deliverability as a continuous learning process that feeds the next stage of scaling.
Every time something broke or underperformed, we treated it as data. We switched registrars. We tested ESP mixes. We added monitoring layers. Each iteration taught us something that made the next configuration better.
That compounding effect is why we could 2x deliverability. There was no single silver bullet. It was switching domain providers, adding reseller account infrastructure, mixing Microsoft and Google, parking IPs, and monitoring inbox placement continuously with tools built for the job.
If you're running cold email at any meaningful volume and your deliverability isn't where it should be, the answer is probably not one thing. It's a stack of decisions, and you need to be willing to test each one.
Key Takeaways
Switch domain providers if you haven't tested registrars as a variable. Porkbun is what we use.
Build a mixed Microsoft and Google sending infrastructure so you have ESP flexibility when one tightens.
Work with reseller accounts to get infrastructure options you won't have on a standard retail setup.
Park your IP address deliberately before sending. Don't let reputation build by accident.
Use a deliverability checker like EmailGuard continuously, not just pre-campaign, and verify placement across Microsoft Outlook and SMTP providers specifically.
Treat every deliverability problem as a data point. The iteration compounds. There is no permanent fix.
Frequently Asked Questions
Why use both Microsoft and Google instead of picking one? Each ESP has its own filtering logic and that logic changes. Running a mix means you have optimization opportunities on both sides and you're not stuck if one provider tightens its rules on cold email. Having both gives you a fallback and a testing environment simultaneously.
What is "parking an IP" and why does it matter for deliverability? Parking your IP means establishing a reputation for that IP before it sends live campaigns. Instead of starting a fresh IP with zero history and immediately hitting inboxes, you let it age and build standing first. It reduces the chance of being flagged as suspicious from day one.
Why is Porkbun specifically being used as a domain registrar? Based on our experience running thousands of sending accounts, Porkbun has proven consistent for cold email domain registration. The cost is low, setup is clean, and the domains perform well at scale. If you haven't tested your registrar as a variable, it's worth doing.
How often should you check deliverability if you're sending at volume? Continuously, not just before a campaign. We use tools like EmailGuard to monitor inbox placement at scale on an ongoing basis. By the time a one-off pre-send check catches a problem, you may have already burned through a sending window.
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