Finally found the right email partner.
“We are incredibly happy with the InboxOS team! These guys are truly the best. They think along completely with our email strategy, spot opportunities before we even see them, and act on them proactively. After multiple collaborations with other email partners, we’ve finally found a party where everything clicks. From strategy and planning to design and copywriting, the level is consistently high across the board. In short: a great, reliable, and above all strong partner we collaborate with full confidence. TOP!”
Nino Sumah · Bukser Jeans
Founder
Feels like an extension of our team.
“The Inbox OS team has been such a great partner for us. They’re incredibly responsive, collaborative, and genuinely invested in our success. What stands out most is their ability to not just execute, but to think strategically and bring ideas forward that actually move the needle. Since working together, we’ve seen a meaningful improvement in our email deliverability, which has had a strong impact on overall performance. It truly feels like working with an extension of our internal team, which is rare. Grateful for the partnership and excited to keep building together.”
Director
Speed and long-term partnership.
“Of all our partners, InboxOS is one of the best to work with. Always superb communication, the whole team is professional, they think along, and what we love most: speed. Everything can be arranged easily and quickly, which ensures a good, streamlined flow for us. As we always say: we prefer to build with partners for the long term, and InboxOS is definitely a partner for the long term.”
Founder
Full Klaviyo overhaul. Immediate results.
“We started working with InboxOS at the beginning of 2024. They completely restructured our Klaviyo account and implemented improvements throughout the year. We’re extremely satisfied with the collaboration: Luc and Cedric are always easy to reach, and if something needs to be done, it gets handled immediately.”
Founder
Professional, results-driven collaboration.
“Thanks to Inbox’s expertise in email marketing and Klaviyo, we achieve great results at Dré Cosmetics. The collaboration is professional and results-driven. During our monthly meetings, we create the planning together and analyze the numbers clearly. This way, we can always make concrete adjustments where needed to achieve maximum results from our campaigns.”
Founder
Email that made an enormous leap.
“Thanks to InboxOS, Dutchies’ email marketing made an enormous leap and our team learned a lot. Luc, Cedric and their team are creative, always come up with a fresh approach, and are directly reachable when something urgent comes up. It’s great to have such an involved and knowledgeable partner alongside our own team.”
Founder
Strategic thinking beyond just campaigns.
“We’ve been working with InboxOS for a while now on our email marketing and are extremely satisfied with the results. The team thinks strategically, looks beyond just campaigns, and has taken our entire email environment to a higher level. Thanks to their structure, optimizations, and flow upgrades, we see clear growth in both revenue and customer engagement. They act fast, communicate clearly, and always come up with smart improvements that truly make an impact.”
Founder
No standard blueprint. They truly listen.
“Since 2024, we’ve been working with Luc from InboxOS and this is one of the best collaborations we have with an external partner. At the start, InboxOS helped with completely restructuring our Klaviyo account during a rebranding from DeMassageWinkel to ZenGrowth. After that, they proactively looked at what works well for our customers and followed through on it. InboxOS doesn’t follow a standard blueprint that can be applied to every business. Instead, they proactively listen along with us and listen to what we (and our customers) want. I don’t know any other agency or freelancer that knows our customers as well as Luc and the rest of the InboxOS team.”
Founder
Finally cracked U.S. email marketing.
“We’re an e-commerce company selling a nighttime syrup in the U.S. market, and for years we struggled to elevate our email marketing despite working with multiple agencies. That changed the moment we started working with Luc and his team. InboxOS brought creativity, strategic thinking, and deep technical expertise to our program. They built a cohesive email strategy that seamlessly supports both prospects and existing customers throughout their entire buying journey. The results have been a clear and measurable ROI. Luc is a true partner: he understands where we are, where we want to go, and always guides us in the right direction. Now, whenever we need email support, we turn to InboxOS. We highly recommend them.”
Founder
Revamped email. Significantly better performance.
“We’ve been working with InboxOS since 2023, and it’s been absolutely great. Their team completely revamped our email marketing, which immediately led to significantly better performance. During sales periods too, we’ve relied on their support for two years now. They’re not only involved but think along to make everything run as smoothly as possible, with demonstrably great results as a consequence. What makes Luc and Cedric special is that they look beyond just email marketing. They’re always willing to share their knowledge and think along at a strategic level, with the goal of growing together.”
Founder
They get our vision and run with it.
“As a young and dynamic company, you’re looking for winners who understand your vision and align with how you work. We came to InboxOS last minute through a mutual connection. From the first contact with Luc, you immediately realize that email marketing is a specialized craft, but above all that his team understands it extremely well. We sell high-ticket products with order values starting at €2,000. InboxOS immediately understood that this requires a unique strategy and clearly maps out what our customers want to know, translating this to the end user in exactly the right way. This has had a direct impact on our sales. The team’s responsiveness is exceptionally fast and they don’t hesitate to make last-minute changes. You can tell they are extremely driven in what they do. For us, a true winner. Highly recommended.”
Founder
A top email marketer. Years of results.
“Luc from InboxOS, a top email marketer. We’ve been working with Luc from InboxOS for years and he’s truly a valued member of our marketing team. His campaigns are well-thought-out, creative, and deliver strong results time after time, from higher open and click rates to real conversions. Luc is reliable, proactively thinks along, and continuously optimizes. He knows exactly how to deploy email marketing effectively, from strategy to execution. An absolute expert and a pleasure to work with. We hope to continue this partnership for a long time!”
Proactive, strategic, and goes the extra mile.
“We’ve been working with InboxOS since 2023 and are still incredibly happy with the collaboration. They’ve helped us set up automated flows, beautiful and strong designs, and creative ideas to improve our email campaigns. What we really appreciate is that InboxOS truly thinks along, shares strategic insights, and goes the extra mile. They’re proactive, respond quickly, and communicate clearly. If you’re looking for an agency that doesn’t just execute but truly thinks along, improves your results, and takes your email marketing to a new, higher level, we highly recommend InboxOS!”
Founder
Proactive team. Tailored to their brand.
“Since January 2025, we’ve been working with the Inbox OS team and we’re extremely satisfied. From the start, they actively think along, are always reachable, and fully tailor their approach to our needs. Thanks to their involvement and expertise, we’ve seen clear improvements in email design, tone of the emails, customer journey, and revenue. Highly recommended for anyone looking for a reliable and proactive email partner.”
Founder
Years of consistent results.
“For several years we’ve been entrusting our email marketing to InboxOS, and we’re still very satisfied. The collaboration with Luc and his team is always pleasant, professional, and effective. They proactively think along, deliver quality, and the results speak for themselves. For us, InboxOS is a reliable partner that we wholeheartedly recommend!”
Founder
Campaigns that speak for themselves.
“Boutoi started working with Inbox-OS fairly recently and the results of our campaigns are undeniable. Clear approach, strategically strong, always going the extra mile, and genuinely willing to brainstorm with you. It truly feels like a team effort.”
Founder
Strategy beyond just sending emails.
“Luc has made huge improvements to our email marketing. It was originally set up by another agency but didn’t deliver much. Now it’s running well and generating great results every month!”
Founder
Professional, knowledgeable, and fast.
“Highly recommend Luc! He is professional, knowledgeable, very easy to work with, and was immediately able to determine our needs and execute on a plan. He really cares about his work and we would definitely use them again!”
Founder
Right knowledge. Fast execution.
“We worked with Inbox-OS as agency Hubrand. Great partner with the right knowledge and they act fast.”
Founder
Great help with campaigns and flows.
“Great collaboration with InboxOS! They’ve been a real help with our email campaigns and flows.”
Founder
Retention marketing experts. Easy to work with.
“It was great to work with Luc and his team, they have a great knowledge of retention marketing and are easy to work with!”
Director
Last-minute Black Friday support. Nailed it.
“Through word of mouth, we found Luc last year, right before Black Friday. We needed short-term support for our email marketing. Despite the limited time, this was not only picked up quickly but also with great care and attention to detail. A real partner you can count on.”
Founder
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