Case Study

How StackOptimise Generated 40+ Leads in 2 Weeks Using Smartlead

Wajahat Ali
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February 24, 2026
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For Felix Frank, founder of StackOptimise and a certified Clay expert, scaling cold email outreach for B2B and SaaS clients in the UK, US, and Europe was a critical challenge. As a sales rep turned agency owner, Felix knew the potential of outbound email but also recognized the limitations of traditional tools like Outreach and HubSpot. He needed a solution to handle high-volume, personalized outreach campaigns without sacrificing quality.

That's when Smartlead came into play. By leveraging Smartlead's powerful cold email marketing tool alongside Clay, Felix and his team built world-class sales-tech systems that drove impressive growth for their clients.

Key Takeaways

  • 9,075 Emails Sent, 5,346 Unique Leads Contacted in two weeks
  • 43 Leads Generated in 2 Weeks
  • 1 Positive Reply for Every 124 Leads Contacted

Challenges Faced Before Smartlead

Felix says, “We were having difficulty reaching out to multiple prospects and scaling our outreach efforts.”

Before adopting Smartlead, Felix and his team faced several obstacles in their cold email outreach efforts: 

Limited Email Volume

Using tools like Outreach and HubSpot, StackOptimise was restricted in the number of emails they could send. Sales reps were limited in how many prospects they could reach, which slowed down lead generation efforts. Felix needed a solution that would allow him to send more emails without compromising quality.

Primary Domain Risk

Felix’s team was using their primary domain for sending email sequences, which posed a risk to their sender's reputation. Sending high volumes of emails from a primary domain increased the chances of emails landing in spam folders, reducing the overall effectiveness of their campaigns.

Lack of Scalability

With existing tools, Felix struggled to scale his outreach efforts. While they could send personalized emails, the process wasn’t scalable enough to meet the growing demands of their B2B and SaaS clients. This limited the agency's ability to generate leads at a faster pace.

How Smartlead Changed Everything 

After switching to Smartlead, Felix saw an immediate transformation in the scalability and efficiency of his cold email outreach campaigns. Here’s how Smartlead helped StackOptimise overcome its challenges:

Higher Volume and Personalized Outreach

Smartlead allowed StackOptimise to significantly increase email volume while maintaining the high-quality personalized approach that Felix’s clients demanded. With unlimited inboxes and rotation features, Felix could send far more emails without risking their sender reputation.

Using Smartlead, StackOptimise sent 9,075 emails to 5,346 unique leads in two weeks, achieving an outstanding one positive reply for every 124 leads contacted. This would have been impossible with their previous tools.

Inbox Rotation and Automation

Felix leveraged Smartlead’s inbox rotation and workflow automation features to optimize email deliverability and ensure that emails landed in the inbox rather than spam folders. This was a game-changer for their outreach campaigns, allowing them to scale efforts without compromising quality.

Smartlead enabled Felix to run six campaigns in just two weeks, generating 43 high-quality leads for his clients. The inbox rotation feature played a critical role in maintaining the scalability of these campaigns.

Centralized Inbox Management

One of Felix’s favorite features was the master inbox provided by Smartlead, which consolidated messages from all email accounts into one centralized location. This feature streamlined operations and made it easier to manage multiple inboxes and monitor campaign performance in real-time.

Smartlead’s mobile app allowed Felix to quickly check campaign progress and update tags in real-time, making it easier to manage outreach efforts on the go.

push leads to new campaigns in one click

Why Felix Frank Loves Smartlead

Felix has highlighted several features that set Smartlead apart from other tools, making it indispensable to his agency’s success:

  • Master Inbox: Consolidates messages from multiple email accounts, making it easier to manage campaigns.
  • Unlimited Inboxes: Provides the scalability needed to run high-volume outreach campaigns without risking sender reputation.
  • Mobile App: Allows real-time monitoring of campaigns, making it easier to track and update outreach efforts from anywhere.
According to Felix, “Smartlead’s combination of automation, unlimited inboxes, and easy campaign management has completely transformed how we run cold email campaigns. We can now scale our efforts and generate results we couldn’t achieve with previous tools.”
Email bounce rate calculator

Conclusion

For Felix Frank and StackOptimise, Smartlead has become essential for executing high-volume, high-quality cold email campaigns. By providing the scalability and personalization needed to drive growth, Smartlead has empowered StackOptimise to generate impressive results for their clients quickly.

Felix’s success story with Smartlead is a testament to the platform’s ability to enhance cold email outreach efforts. The platform allows agencies to scale their lead generation efforts while maintaining personalized communication with prospects.

If you're looking for similar results for your business, Smartlead is there to make that a reality. How? You can find that yourself with a free 14-day trial from right here.

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Wajahat Ali

Wajahat Ali is a Technical Content Writer at Smartlead, specializing in the B2B and SaaS sectors. With a talent for simplifying complex concepts, he crafts clear, engaging content that makes intricate topics accessible to both experts and newcomers. Wajahat’s expertise spans across copywriting, social media content, and lead generation, where he consistently delivers valuable, impactful content that resonates with a global audience. His ability to blend technical knowledge with compelling storytelling ensures that every piece of content drives both understanding and results, helping businesses connect with their target markets effectively.

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Frequently asked questions

What is Smartlead's cold email outreach software?
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Smartlead's cold email outreach tool helps businesses scale their outreach efforts seamlessly. With unlimited mailboxes, fully automated email warmup functionality, a multi-channel infrastructure, and a user-friendly unibox, it empowers users to manage their entire revenue cycle in one place. Whether you're looking to streamline cold email campaigns with automated email warmups, personalization fields, automated mailbox rotation, easy integrations, and spintax, improve productivity, or enhance scalability with subsequences based on lead’s intentions, automated replies, and full white-label experience, our cold email tool implifies it in a single solution.

How does Smartlead's unlimited mailboxes feature benefit me?
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Our "unlimited mailboxes" feature allows you to expand your email communications without restrictions imposed by a mailbox limit. This means you won't be constrained by artificial caps on the number of mailboxes you can connect and use. This feature makes Smartlead the best cold email software and empowers you to reach a wider audience, engage with more potential customers, and manage diverse email campaigns effectively.

What do you mean by "unibox to handle your entire revenue cycle"?
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The "unibox" is one of the unique features of Smartlead cold email outreach tool, and it's a game-changer when it comes to managing your revenue cycle. The master inbox or the unibox consolidates all your outreach channels, responses, sales follow-ups, and conversions into one centralized, user-friendly mailbox.

With the "unibox," you gain the ability to:
1. Focus on closing deals: You can now say goodbye to the hassle of logging into multiple mailboxes to search for replies. The "unibox" streamlines your sales communication, allowing you to focus on what matters most—closing deals.

2. Centralized lead management: All your leads are managed from one central location, simplifying lead tracking and response management. This ensures you take advantage of every opportunity and efficiently engage with your prospects.

3. Maintain context: The "unibox" provides a 360-degree view of all your customer messages, allowing you to maintain context and deliver more personalized and effective responses.

Can Smartlead help improve my email deliverability rates?
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Yes, our cold emailing software is designed to significantly improve your email deliverability rates. It enhances email deliverability through AI-powered email warmups across providers, unique IP rotating for each campaign, and dynamic ESP matching.

Real-time AI learning refines strategies based on performance, optimizing deliverability without manual adjustments. Smartlead's advanced features and strategies are designed to improve email deliverability rates, making it a robust choice for enhancing cold email campaign success.

Can I integrate Smartlead with other tools I'm using?
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Certainly, Smartlead cold email tool is designed for seamless integration with a wide range of tools and platforms. Smartlead offers integration with HubSpot, Salesforce, Pipedrive, Clay, Listkit, and more. You can leverage webhooks and APIs to integrate the tools you use. Try Now!

What is Smartlead, and how can it enhance my cold email campaigns?
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Smartlead is a robust cold emailing software designed to transform cold emails into reliable revenue streams. Trusted by over 31,000 businesses, Smartlead excels in email deliverability, lead generation, cold email automation, and sales outreach. A unified master inbox streamlines communication management, while built-in email verification reduces bounce rates.Additionally, Smartlead offers essential tools such as CNAME, SPF Checker, DMARC Checker, Email Verifier, Blacklist Check Tool, and Email Bounce Rate Calculator for optimizing email performance.

How does Smartlead, as a cold emailing tool, automate the cold email process?
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Smartlead’s robust cold email API and automation infrastructure streamline outbound communication by transforming the campaign creation and management processes. It seamlessly integrates data across software systems using APIs and webhooks, adjusts settings, and leverages AI for personalised content.

The cold emailing tool categorises lead intent, offers comprehensive email management with automated notifications, and integrates smoothly with CRMs like Zapier, Make, N8N, HubSpot, Salesforce, and Pipedrive. Smartlead supports scalable outreach by rapidly adding mailboxes and drip-feeding leads into active campaigns Sign Up Now!

How does Smartlead ensure my emails don't land in the spam folder?
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Smartlead, the best cold email marketing tool, ensures your emails reach the intended recipients' primary inbox rather than the spam folder.

Here's how it works:
1. Our "unlimited warmups" feature is designed to build and maintain a healthy sending reputation for your cold email outreach. Instead of sending a large volume of emails all at once, which can trigger spam filters, we gradually ramp up your sending volume. This gradual approach, combined with positive email interactions, helps boost your email deliverability rates.

2. We deploy high-deliverability IP servers specific to each campaign.

3. The ‘Warmup’ feature replicates humanized email sending patterns, spintax, and smart replies.

4. By establishing a positive sender reputation and gradually increasing the number of sent emails, Smartlead minimizes the risk of your emails being flagged as spam. This way, you can be confident that your messages will consistently land in the primary inbox, increasing the likelihood of engagement and successful communication with your recipients.

What features does Smartlead offer for cold email personalisation?
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Smartlead enhances cold email personalisation through advanced AI-driven capabilities and strategic integrations. Partnered with Clay, The cold remaining software facilitates efficient lead list building, enrichment from over 50 data providers, and real-time scraping for precise targeting. Hyper-personalised cold emails crafted in Clay seamlessly integrate with Smartlead campaigns.

Moreover, Smartlead employs humanised, natural email interactions and smart replies to boost engagement and response rates. Additionally, the SmartAI Bot creates persona-specific, high-converting sales copy. Also you can create persona-specific, high-converting sales copy using SmartAI Bot. You can train the AI bot to achieve 100% categorisation accuracy, optimising engagement and conversion rates.

Is Smartlead suitable for both small businesses and large enterprises?
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Smartlead accommodates both small businesses and large enterprises with flexible pricing and comprehensive features. The Basic Plan at $39/month suits small businesses and solopreneurs, offering 2000 active leads and 6000 monthly emails, alongside essential tools like unlimited email warm-up and detailed analytics.

Marketers and growing businesses benefit from the Pro Plan ($94/month), with 30000 active leads and 150000 monthly emails, plus a custom CRM and active support. Lead generation agencies and large enterprises can opt for the Custom Plan ($174/month), providing up to 12 million active lead credits and 60 million emails, with advanced CRM integration and customisation options.