How Limelight Scaled Its Outbound on Smartlead Without Breaking Deliverability

Limelight did not come to Smartlead looking for a cold email tool. It came looking for infrastructure it could trust with everything.

As an AI employee company powering influencer marketing, customer advocacy, employee social, and social listening for marketing leaders at mid-sized and enterprise B2B companies, Limelight had a use case more complex than most.

It needed Smartlead not just for outbound campaigns but to power the cold email layer underneath its own customer marketplace. Two different use cases. One platform. The whole operation depending on it.

David Walsh, CEO and Co-Founder of Limelight, chose Smartlead because it was the only platform flexible enough to handle both.

In the three years since, Limelight has scaled from 20 inboxes to 200 warmed-up and ready to send in under three weeks, gone from 500 emails a week to 9,000, run four simultaneous campaign types against the same ICP, and hit reply rates as high as 20% on well-constructed sequences.

Who Is Behind Limelight?

David Walsh is not a first-time founder testing ideas.

He is a three-time founder who has raised over $30 million across his ventures, scaled companies past 100 employees, and chosen to apply everything he learned in revenue technology to a problem most B2B marketing leaders have not yet solved.

His latest company, Limelight, is building the AI-powered marketing workforce for B2B companies, with AI employees that handle influencer marketing, customer advocacy, employee social, and social listening across the hardest channels to scale.

What makes Limelight distinct is where it sits in the stack.

Most marketing platforms give leaders more tools to operate. Limelight gives them AI employees to operate those tools for them.

Backed by Ascend VC and SNR Capital in a $2 million seed round, the company serves heads of marketing at mid-cap and enterprise B2B SaaS companies with more than $20 million in revenue, specifically the buyers who feel the gap between the channels they need to activate and the team bandwidth they actually have.

The cold outbound operation sits underneath all of it. Without reliable cold email deliverability that held at volume, the marketplace could not function and the outbound engine would stall.

The Dual Use Case That Made the Platform Decision Challenging

Most companies using a cold email platform have one job for it: send outbound sequences.

Limelight had two. The first was standard cold email sequences targeting heads of marketing at mid-cap and enterprise B2B SaaS companies.

The second was more unusual, powering the cold email infrastructure underneath Limelight's own influencer marketplace, where a separate set of warmed-up inboxes needed to consistently deliver at a different standard from the outbound domains.

Two distinct infrastructure requirements.

Two different warmup statuses. Two different delivery needs. And the expectation that both could be managed, segmented, and monitored inside a single platform without chaos. Finding a platform that could handle that complexity was what made the decision both harder and more consequential.

How Limelight Found Smartlead

The relationship between Limelight and Smartlead began not with a product demo but with a customer deal.

Smartlead became a Limelight customer for influencer marketing first. When David later began evaluating cold email platforms seriously, that existing relationship gave him a layer of trust most vendors had to earn from scratch.

He also noticed Smartlead's growing presence in the B2B community, where the platform was increasingly cited by founders and GTM teams on LinkedIn as the default choice for serious outbound work.

"Smartlead became a customer of ours actually for influencer marketing. And then through that relationship, when we were assessing cold outbound companies, we realized that Smartlead was the right company for us. Smartlead is everywhere these days. People talk about it on LinkedIn a lot. And I feel like I am connected to your team in a few different ways. Your social presence is probably what drew me." - David Walsh, CEO and Co-Founder, Limelight

When the formal evaluation began, three criteria mattered most: cold email deliverability, infrastructure flexibility, and platform consolidation. Smartlead came out ahead on all three.

Every cold email platform makes deliverability promises.

David's filter was not which platform had the best marketing copy around inbox placement. It was which platform he could trust at volume, not at 10 or 20 sends, but at thousands of emails a day across hundreds of inboxes powering a live marketplace.

"Number one is always deliverability. Every single email company that we looked at, the thing we cared most about is: are we confident their emails will get into the inbox? We have a marketplace and we use Smartlead to also power our marketplace as well as doing outbound emails. For the marketplace approach, we needed a flexible infrastructure that allowed us to send thousands of emails a day. Smartlead was the best we looked at because of its flexibility and the way we could set it up and connect it to our system."

Why Consolidation Closed the Decision

One factor that many founders overlook when evaluating email outreach automation platforms is how much operational complexity lives outside the tool itself.

Domain purchasing, warmup management, inbox segmentation, and analytics: when these are split across multiple tools, the administrative overhead compounds quickly. Smartlead collapsed the stack into a single place.

"We could actually purchase and buy the domains, which made it much easier for us to stay in control."

The Market Limelight Serves

Limelight operates at the intersection of two worlds that most companies treat as separate: outbound pipeline generation and influencer-led inbound growth.

Its clients are heads of marketing at mid-cap and enterprise B2B SaaS companies who need to activate channels that are genuinely hard to scale without dedicated operational infrastructure.

The ICP is precise: companies over $20 million in revenue, across all verticals, where the marketing leader is accountable for results on channels their team does not yet have established playbooks for.

These are sophisticated buyers who have tried to build influencer programmes manually and found that spreadsheets, direct messages, and guesswork do not hold at scale.

Smartlead powers both sides of Limelight's cold email operation. The outbound campaigns target heads of marketing directly, running multiple simultaneous sequences against the same ICP with different copy angles AB tested in parallel.

The marketplace emails run on a separate cohort of inboxes that are already fully warmed and consistently delivering, with a different operational standard from the domains still in warmup.

Both cohorts live inside the same Smartlead account. Segmented clearly. Visible from a single login. Manageable without switching between platforms or manually reconciling data from separate systems.

The Challenges Smartlead Solved for Limelight

Scaling a cold email operation is straightforward until it is not.

The complexity tends to emerge at a specific threshold: the point where the number of inboxes, the volume of sequences, and the diversity of use cases outgrow what most platforms were designed to handle.

Limelight hit that threshold fast, and the platforms it had tried before Smartlead did not hold up when volume grew.

Scaling Infrastructure Without Losing Deliverability or Adding Overhead

The previous platforms David evaluated worked adequately at low volumes. At scale, they broke down in two specific ways: deliverability degraded and administrative overhead increased proportionally with the number of inboxes.

problem was acceptable for a company whose marketplace depended on the email layer functioning reliably.

"Most of our open email infrastructure was not customizable for what we needed. We were not confident in its ability to scale. It was great for 10, 20 emails, but when you start to scale to hundreds of cold outbound inboxes needing to be warmed up, the infrastructure that exists with other platforms does not scale. It is more cumbersome and more administrative work. With Smartlead it is just turnkey and you can bulk action all of your inboxes." - David Walsh, CEO and Co-Founder, Limelight

Moving From 20 to 200 Inboxes in Under Three Weeks

The most concrete proof of Smartlead's infrastructure capability is the speed at which Limelight scaled.

from 20 inboxes and needing to reach full operational capacity quickly, Limelight used Smartlead's email warmup infrastructure to get to 200 warmed-up inboxes ready for live outbound in less than three weeks.

That pace is not achievable on platforms where warmup requires manual per-domain configuration.

"We went from 20 inboxes to something like 200 inboxes warmed up and ready to do outbound within the space of two to three weeks. And once we scaled that, we scaled up the ability to send 9,000 emails a week as the threshold." - David Walsh, CEO and Co-Founder, Limelight

Managing Two Infrastructure Cohorts Without Operational Chaos

Limelight's dual use case required genuine inbox segmentation: outbound domains still in warmup in one cohort, marketplace domains already live and delivering in another.

Without the ability to segment and manage these separately inside one account, the operational complexity would have required a second platform or constant manual reconciliation.

"We love the ability to log into hundreds of accounts at once and be able to segment those accounts into different cohorts. We have cold email outbound domains being warmed up in one cohort. We have another cohort, which is our marketplace emails that we are confident have already been warmed up and are constantly delivering to the inbox."

Seeing Everything in One Place Without Manual Account Switching

At 9,000 emails a week across four campaign types and 50 inboxes, visibility is an operational problem as much as it is an analytical one.

David needed a way to understand which sequences were performing, which were not, and which copy angles were generating the highest response rates, without logging into each inbox account individually and manually aggregating the data. Smartlead's unified master inbox gave him exactly that view.

"The master inbox feature was something I was not aware of until I started to really use it. I can log in quickly and see and navigate through a master inbox, all of the response rates. I can quickly see which emails are performing, which are underperforming, what sequences are getting the highest response rates. That bird's eye view of seeing everything in one place allows me to quickly identify what is working and what is not working."

Getting Real Answers to Complex Technical Questions Without a Weekly Call

Limelight's setup was not standard, and the questions it raised were not standard either. David needed a support experience that provided substantive, data-backed answers to complicated infrastructure questions, without requiring a scheduled account management relationship to access that information.

"We had a lot to lose and a lot at stake. I felt like we could communicate and get a lot of data and insights directly from your customer support agents, which helped make the decision to move forward and continue using Smartlead. You had a lot of data and a lot of answers to complicated questions at our fingertips. I personally like not having to have an account management call every week. I would rather just access the data instantly. And that is what we get from Smartlead."

Campaign Results: 9,000 Emails a Week and Up to 20% Reply Rates

Numbers tell part of the story.

The context behind them tells the rest. When Limelight scaled from 500 to 9,000 weekly sends, it was not simply sending more of the same email to more people.

It was running four different copy types and four campaign variations simultaneously against the same ICP, using Smartlead's analytics layer to understand what was resonating and cut what was not.

That level of AB testing discipline at volume is only possible when the underlying infrastructure is stable enough to isolate variables cleanly.

The results across those campaigns varied, as any honest account of cold email performance will. S

ome sequences found the right combination of message, timing, and audience. Some did not. But the top performers delivered reply rates that most cold email operations do not reach, and the analytics made it clear which ones deserved further investment.

"We went from the ability to send 500 emails a week to 9,000 a week, across four different campaigns with 30 to 50 inboxes. That scale allowed us to collect a lot more information and data and identify what was resonating and what was not."

"There were some email campaigns that had over 10% response rates, which was awesome. Some even 20% response rates if set up correctly. The confidence that we are going to find the right person, send the right message, and that Smartlead will deliver to their inbox is how we are able to increase our deliverability and response rates."

David Walsh, CEO and Co-Founder, Limelight

How Smartlead Solved Limelight's Challenges

Every platform makes promises at the point of sale.

What matters is how those promises hold when the operation is running at full load, the infrastructure is complex, and the margin for error is low. For Limelight, the test of Smartlead was not the onboarding experience.

It was the moment the marketplace went live on the same account as the outbound campaigns, and both needed to perform simultaneously without degradation.

Cold Email Deliverability Infrastructure That Holds at Volume

The foundational reason Limelight chose Smartlead and has stayed. Confidence that emails land in the inbox at scale, not just at 10 to 20 sends, but at 9,000 a week across 200 inboxes. Learn more about Smartlead's deliverability infrastructure.

Domain purchasing inside the platform gave Limelight full infrastructure control without managing external registrars.

Inbox Cohort Segmentation and Unlimited Mailboxes

The ability to segment hundreds of inboxes into distinct cohorts, each with different warmup status and delivery configurations, made Limelight's dual use case operationally viable. Outbound warmup domains in one group. Live marketplace domains in another. Both visible and manageable inside one account without manual reconciliation. See how unlimited mailboxes work on Smartlead.

Unified Master Inbox

The feature David did not anticipate mattering as much as it did. At 9,000 sends a week across four campaign types and 50 inboxes, the master inbox became the central operational view of the entire operation. Reply rates per sequence, performance comparisons across campaigns, identification of underperforming copy: all visible in one place without switching accounts.

Email Sequencing Built for Sophisticated Multi-Step Logic

Running four simultaneous sequences, each targeting the same ICP with a different copy angle, requires a sequencing tool that does not create friction between strategy and execution. Smartlead's sequence builder was the clearest differentiator David found across all the platforms he evaluated.

"Email sequencing is very easy and convenient to set up sophisticated sequences in the platform. I have looked at all the other tools and Smartlead was by far the best at setting those up and making it easy for me to run multiple sequences at once."

Analytics and Metrics Across All Running Campaigns

Campaign-level and inbox-level performance data across all active sequences. The analytics layer that made running four copy types at 9,000 sends per week actionable rather than just ambitious. Read how other companies have used Smartlead's analytics to scale their results on the Smartlead case studies page.

"All of the metrics and analytics that you provide are best in the industry right now."

Support With Real Data for Complex Technical Questions

Smartlead's support gave Limelight substantive answers backed by real data, not generic troubleshooting guides.

That depth of information, accessible on demand rather than through a scheduled call, was a meaningful factor in the decision to commit the entire marketplace infrastructure to the platform.

Notable Achievements

• Scaled from 20 to 200 warmed-up inboxes ready for outbound in under three weeks on Smartlead
• Increased weekly send volume from 500 to 9,000 emails across four simultaneous campaign types
• Hit reply rates of 10% to 20% on best-performing sequences with cold email deliverability maintained throughout
• Ran four different copy types and four campaign variations simultaneously against the same ICP, using Smartlead's AB testing analytics to identify what resonated
• Powered two entirely separate cold email infrastructure cohorts from a single Smartlead account: outbound warmup domains and live marketplace delivery domains
• Purchased and managed all sending domains directly inside Smartlead, keeping full infrastructure control consolidated
• Used Smartlead's unified master inbox to monitor reply rates and sequence performance across 30 to 50 simultaneous inboxes

What Comes Next for Limelight

David's vision for where Smartlead goes next is not a feature request.

It is a product category suggestion: build the AI SDR layer directly on top of the infrastructure that already exists, and connect it to the LLMs that founders are already using every day.

The suggestion is grounded in David's own experience as both a Smartlead customer and a founder building AI employees: if the platform can already handle the backend infrastructure reliably, the logical next step is to automate the front end as well.

For Limelight, the near-term priority is continuing to scale the outbound operation and deepen the marketplace email infrastructure. For David personally, the goal is the same one every founder with a complicated setup shares: more performance, less administration, and a platform that does more of the work on his behalf.

David's advice for any company evaluating cold email platforms is unambiguous. It is advice he has arrived at through real experience with the consequences of getting it wrong, on platforms that could not scale, that burned inboxes, and that added overhead instead of removing it.

"Outbound is complicated and it is getting more challenging and the rules have changed. Use a system that you trust that has the domain expertise and the capabilities to ensure they are compliant and that things are set up the correct way. One small mistake in setup will dramatically reduce your cold email deliverability and potentially burn your inboxes. Use Smartlead. The cost is very affordable for the value that you bring. It is not only a premium product, it is priced accordingly. And I would be willing to pay and advise startups to use the product."