Hiring an in-house SDR is expensive, time-consuming, and risky. These five agencies handle your cold email outreach from start to finish — infrastructure, lead sourcing, copywriting, deliverability, and reply management — so you can book meetings without the overhead. Each
Why B2B Companies Are Ditching In-House SDRs for Cold Email Agencies
The traditional SDR model is broken. High turnover, long ramp times, and escalating salaries make hiring an in-house SDR a risky bet. That's why a growing number of B2B companies are turning to cold email agencies that act as direct SDR replacements. These firms handle the entire outbound process — from building email infrastructure and sourcing leads to writing copy, managing deliverability, and replying to prospects. The result: predictable pipeline growth at a fraction of the cost. The agencies in this roundup have proven they can deliver qualified meetings month after month, often on a flat retainer. For any B2B company looking to scale outbound without the headache of hiring, this model is a game-changer.
How We Ranked the Top Cold Email Agencies
We evaluated each agency based on five key criteria: (1) track record of delivering qualified meetings and pipeline revenue, (2) breadth of services (infrastructure, copy, deliverability, reply management), (3) pricing transparency and value relative to an in-house SDR, (4) client reviews and longevity in the market, and (5) specialization in cold email as a primary channel. All five agencies are direct competitors to Horizon and operate in the US B2B market.
Here's a quick comparison of the five agencies that can replace your SDR team. Each one offers a done-for-you cold email solution, but they differ in scale, pricing, and focus.
| Provider | Best For |
|---|---|
| Belkins | Companies that want a proven, full-stack outbound engine with a strong track record |
| SalesHive | Businesses that want AI-driven outbound with US-based SDRs and no long-term commitment |
| Cleverly | Companies that prioritize hyper-personalized outreach and measurable ROI |
| Horizon | B2B companies that want a cost-effective, hands-on SDR replacement with a personal touch |
| Outbound Sales Pro | Companies that want a multi-channel outbound approach with proprietary deliverability tools |
The Top 5 Cold Email Agencies for B2B Pipeline Growth
#1 Belkins
A screenshot of the Belkins website.
Belkins is an award-winning B2B cold email and lead generation agency that delivers a full-stack outbound solution. They handle everything from email infrastructure and copywriting to deliverability and reply management, positioning themselves as a complete SDR replacement. With a track record of 100–400+ qualified appointments per year per client, Belkins is a proven choice for companies serious about pipeline growth. Their US-led team with global delivery ensures quality while keeping costs competitive. If you want a polished, scalable operation that's been vetted by hundreds of B2B brands, Belkins is the gold standard. Check their cold email services page for specifics.
#2 SalesHive
A screenshot of the SalesHive website.
SalesHive combines AI-powered tools with US-based SDRs to run cold email and cold calling campaigns on their proprietary platform. With over 10 years in business and 2,285+ clients, they bring serious scale and experience to the table. Their no-long-term-contracts model gives you flexibility, and their platform provides real-time visibility into campaign performance. SalesHive is a direct competitor to Horizon, offering the same SDR replacement positioning with a tech-forward twist. If you want a blend of human touch and automation, SalesHive is a strong contender. Learn more about their email outreach approach on their site.
#3 Cleverly
A screenshot of the Cleverly website.
Cleverly is a B2B lead generation agency that specializes in hyper-personalized cold email, LinkedIn, and cold calling campaigns. Trusted by over 10,000 B2B companies, they've generated more than $312 million in client pipeline. Their ROI-focused approach means every campaign is built to maximize meetings and revenue, not just vanity metrics. Cleverly's done-for-you model covers targeting, copywriting, and deliverability, making it a direct competitor in the outbound space. If you need a partner that obsesses over personalization and results, Cleverly delivers. Visit their cold email outreach agency page for details.
#4 Horizon
A screenshot of the Horizon website.
Horizon is an outbound sales firm that builds cold email campaigns and replaces in-house SDRs with a cost-effective alternative. They provide the full infrastructure — lead sourcing, sequence execution, and reply management — so you can focus on closing deals. Horizon positions itself as a lean, no-frills option for B2B companies that want to book meetings without the overhead of hiring and training an SDR. Their approach is straightforward: deliver pipeline growth through targeted cold email outreach. If you're looking for a smaller, more agile partner that treats your account with high attention, Horizon is worth a look. Check their website for more on their SDR replacement model.
#5 Outbound Sales Pro
A screenshot of the Outbound Sales Pro website.
Outbound Sales Pro positions itself as an outsourced SDR agency at a fraction of the cost of hiring an in-house SDR — messaging nearly identical to Horizon's. They use a multi-channel approach that includes cold email, LinkedIn outreach, website visitor identification, and real-time calls. Their proprietary Parakeet email infrastructure helps ensure high deliverability and reply management. Outbound Sales Pro is a direct competitor in the done-for-you outbound space, offering a comprehensive solution for companies that want to scale their pipeline without adding headcount. If you need a multi-channel outbound engine with a proven infrastructure, this agency fits the bill. See their services page for details.
How to Choose the Right Cold Email Agency for Your Business
Start by defining your budget and expected meeting volume. If you need a proven, large-scale operation, Belkins or SalesHive are safe bets. If hyper-personalization is your priority, Cleverly stands out. For a lean, cost-effective option with a personal touch, Horizon is a strong choice. And if you want multi-channel outreach with proprietary tech, Outbound Sales Pro delivers. Always ask about their lead sourcing process, deliverability rates, and how they handle reply management. Request case studies specific to your industry. And remember: the best agency is one that aligns with your sales cycle and target account list.
Automating Your Outbound Workflow with These Agencies
All five agencies integrate with your CRM to sync leads, track replies, and update pipeline stages. Typically, you'll provide a target list or ICP, and the agency handles the rest: setting up email infrastructure (SPF, DKIM, DMARC), warming up domains, writing sequences, and managing replies. Some, like SalesHive, offer a proprietary platform with real-time dashboards. Others, like Belkins, provide regular reporting via email or shared tools. The goal is to create a seamless flow where you only step in when a prospect books a meeting. This automation frees your sales team to focus on closing, not prospecting.
The Bottom Line on SDR Replacement Agencies
Cold email agencies are no longer a niche experiment — they're a proven way to scale outbound without the overhead of an in-house team. Each of the five agencies listed here has a track record of delivering meetings and pipeline for B2B companies. Whether you choose the scale of Belkins, the AI edge of SalesHive, the personalization of Cleverly, the cost-effectiveness of Horizon, or the multi-channel approach of Outbound Sales Pro, you're getting a partner that treats your pipeline as seriously as you do. The key is to pick the one that fits your budget, culture, and growth goals. Start with a pilot campaign and measure results before scaling.