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Home/The SaaS Podcast/Episode 456
How Mailtrap Found Product-Market Fit With Zero Marketing
Sergiy Korolov, Mailtrap

How Mailtrap Found Product-Market Fit With Zero Marketing

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Episode Summary

In 2011, Sergiy Korolov's team accidentally sent 20,000 test billing emails to real customers. The chaos was immediate - customers confused about whether they'd been charged. So they built a small internal tool to prevent it from happening again. What followed was an accidental product-market fit story that most founders only dream about.

When they shared the tool with the Ruby on Rails community, developers loved it. Mailtrap spread purely through word of mouth, eventually attracting more than 200,000 users - all with zero marketing spend.

Sergiy Korolov is the co-CEO of Railsware, a product studio that helps companies design, build, and scale successful software products, and the co-founder of Mailtrap, an email testing and delivery platform trusted by developers worldwide.

Back in 2011, Sergiy's team made a massive mistake.

They accidentally sent 20,000 test billing emails from their staging environment straight to real customers. The chaos was immediate. Customers were confused and upset, wondering if they'd actually been charged or not.

To make sure it never happened again, they built a small internal tool to stop test emails from reaching real inboxes.

When they shared it with the Ruby on Rails community, something unexpected happened. Developers loved it, and Mailtrap spread purely through word of mouth, eventually attracting more than 200,000 users.

For the next five years, Mailtrap stayed free.

It was a side project until 2016, when Sergiy finally decided to turn it into a real business. Instead of guessing, his team ran over 100 customer interviews and dug into usage data to guide pricing and product decisions.

It took another four years to reach $1 million in ARR.

Growth was slow and steady, not the overnight success story people imagine. And just as things started to pick up, a new challenge appeared. Customers wanted Mailtrap to handle production email sending too. That meant turning a product built to avoid sending emails into one that had to deliver them flawlessly.

It was a risky move.

The shift created a whole new set of problems, from dealing with spam attacks and deliverability issues to fighting brand confusion about what Mailtrap actually did. Suddenly, a product known for blocking emails had to prove it could deliver them reliably.

Sergiy and his team spent months rebuilding their infrastructure, tightening security, and designing tools that gave developers more visibility and control. It wasn't glamorous work, but it paid off. Mailtrap evolved into a trusted, full-stack email platform used by teams around the world.

Today, Mailtrap generates seven-figure ARR with a 40-person team and more than 100,000 monthly active users.

Topics: Product-Led Growth|Product-Market Fit|Pricing & Monetization

Key Insight

Mailtrap co-founder Sergiy Korolov grew to 200,000 users over five years with zero marketing spend by sharing an internal developer tool with the Ruby on Rails community. After finding product-market fit organically, his team ran over 100 customer interviews and combined qualitative feedback with product analytics to guide pricing, reaching $1M ARR by 2020.

Key Ideas

  • Mailtrap was born from a 20,000-email staging disaster in 2011 and shared with the Ruby on Rails community where the team was already active
  • The tool attracted 200,000 signups with zero marketing budget over five years before any monetization attempt
  • Mandatory signup surveys with randomized answers had zero impact on activation rates but revealed which user cohorts actually convert to paid
  • A fake door test for email campaigns generated 300 survey responses in weeks without building any code or offering incentives
  • Transitioning from email testing to email sending required fighting brand confusion among millions of users who associated Mailtrap with blocking emails

Key Lessons

  • 🎯 Product-market fit can come from solving your own pain: Mailtrap was born from a 20,000-email staging disaster. Building a tool that fixed their own problem created authentic product-market fit that resonated with the entire Ruby on Rails developer community.

  • 🚀 Community trust drives product-led growth faster than paid marketing: Sergiy's team was already active in the Ruby on Rails community before sharing Mailtrap. That existing trust turned developers into organic promoters who grew the user base to 200,000 with zero marketing spend.

  • 💰 Run 100+ customer interviews before setting your SaaS pricing: Instead of guessing, Mailtrap interviewed users across segments and matched qualitative feedback with product analytics to find which features correlated with paid conversion - building pricing around real willingness to pay.

  • 📊 Mandatory signup surveys reveal your real ICP without hurting activation: Mailtrap added required clickable questions about intent, role, and channel during signup. Activation rates stayed flat, but the team could finally filter analytics by cohort and show marketing which segments actually drive revenue.

  • 🛠️ Validate features with fake door tests before writing code: When users requested email campaigns, Mailtrap added a menu item linking to a survey instead of a feature. They collected 300 responses in weeks with zero incentives - proving demand and gathering prioritization data without any development cost.

  • 📉 Product-market fit can break when you expand too broadly: Mailtrap's move from email testing to email sending created brand confusion among millions of users. A product known for blocking emails had to rebuild trust and convince developers it could also deliver them reliably.

  • 🔄 Fewer clicks does not mean higher conversion: Mailtrap streamlined their first-time experience assuming it would boost activation. The change was barely noticeable - proving that users tolerate friction when they understand the value waiting on the other side.

Watch the Episode

Chapters

00:00Introduction
00:25Railsware: The Product Studio Behind Mailtrap
02:29What Mailtrap Does and the Problem It Solves
02:43The 20,000 Email Disaster That Started Everything
03:44Sharing With the Ruby on Rails Community
05:30From Internal Tool to Growing User Base
06:11Building the 40-Person Mailtrap Team
08:29Why Mailtrap Stayed Free for Five Years
10:37Pricing Strategy and the First Paid Plans
11:00Running 100+ Customer Interviews for Pricing
13:40The Surprising Onboarding Experiment
15:10Why Fewer Clicks Did Not Boost Conversion
17:22Reaching $1M ARR by 2020
17:59The Mandatory Signup Survey That Changed Everything
21:05Filtering Analytics by User Cohort and Intent
22:5530,000 Monthly Signups and Zero Drop From Surveys
24:45Randomizing Survey Answers to Eliminate Bias
26:02The Fake Door Test for Email Campaigns
28:30Expanding From Email Testing to Email Sending
29:03Fighting Spam and Building Deliverability Infrastructure
31:16The Brand Perception Challenge
33:04Learning From Competitor Weaknesses
35:10Building Better Analytics and Drill-Down Dashboards
36:37AI and Vibe Coding: Hype vs. Reality for Developers
43:24When Vibe-Coded Products Need Professional Engineers
47:45Lightning Round
47:58Best Business Advice: Go With the Flow
48:03Book Recommendation: The Power of Now
49:08Key Founder Trait: Never Stop
49:21Favorite Productivity Tool: Spotlight and Command Lines
50:35Fun Fact: Former Olympic Reserve Swimmer
50:57Passions Outside Work: Sports and Family

Episode Q&A

How did Mailtrap find product-market fit with zero marketing spend?

Sergiy Korolov's team shared their internal email testing tool with the Ruby on Rails community where they were already active contributors. Developers spread it through word of mouth because it solved a universal pain point, growing Mailtrap to 200,000 users without any paid acquisition.

Why did Mailtrap stay free for five years before monetizing?

The team treated it as a side project while focusing on their consultancy business at Railsware. They only decided to monetize when feature requests kept growing and they realized the product could sustain a real business with dedicated resources.

How did Sergiy Korolov use 100+ customer interviews to set Mailtrap's pricing?

His team interviewed users across different segments - small companies, enterprises, and individuals - and combined qualitative feedback with product analytics to identify which features correlated with willingness to pay, then built the pricing model around those insights.

What happened when Mailtrap tested reducing signup friction?

Sergiy's team assumed that removing clicks from the first-time experience would dramatically increase conversion. The result was barely noticeable - proving that users will tolerate extra steps if they understand the core value they will reach.

How did Mailtrap validate product-market fit for email campaigns before building the feature?

They added an "Email Campaigns" menu item that led to a Typeform survey instead of a working feature. Without offering any incentives, they received 300 responses in weeks - confirming demand and collecting feature prioritization data before writing a single line of code.

Why did Mailtrap's mandatory signup survey not hurt conversion rates?

Sergiy kept the survey to three clickable steps with no open-ended questions and randomized answer positions to eliminate bias. Conversion from signup to activation stayed exactly the same while giving the team powerful cohort filtering for marketing decisions.

What was the biggest challenge when Mailtrap expanded from email testing to sending?

Brand perception - millions of users knew Mailtrap as a tool that blocks emails from reaching real inboxes. Convincing them it could also reliably deliver production emails required months of repositioning and trust-building with the developer community.

How did Sergiy Korolov identify product-market fit signals in Mailtrap's analytics?

By filtering mandatory survey data by user intent, role, and country, his team discovered that business-intent C-level users from specific regions converted at dramatically higher rates than pet project users - revealing the true ICP hidden inside hundreds of thousands of signups.

What competitive advantage did Mailtrap build over SendGrid and Mailgun?

After experiencing poor deliverability analytics in existing tools firsthand, Sergiy's team built drill-down dashboards that let developers see helicopter-view metrics and click deeper to find root causes of delivery issues - solving the visibility gap competitors ignored.

Book Recommendations

The Power of Now

by Eckhart Tolle

A New Earth

by Eckhart Tolle

Links

  • Mailtrap: Website | LinkedIn | X
  • Sergiy Korolov: LinkedIn | X
  • Omer Khan: LinkedIn | X
Full Transcript

[00:00:00] Omer Khan:
Sergey, welcome to the show.

[00:00:01] Sergiy Korolov:
Hi Omer, nice to meet you and I'm glad to be here.

[00:00:05] Omer Khan:
Do you have a favorite quote? Something that inspires or motivates you?

[00:00:10] Sergiy Korolov:
So I have one which sounds like master your craft every day. So we consider ourselves as a craftsman, me, myself and my partner Yaroslav and all the team that we have. So master a craft every day.

[00:00:25] Omer Khan:
Great. So you are the co CEO of Railsware and then also the co founder of Mailtrap as well as some other products. We're going to spend most of the conversation today talking about Mailtrap and how you built that business, but tell us a little bit about how things fit in with Railsware and all the other products that you work on.

[00:00:45] Sergiy Korolov:
Yeah, so Railsware is the product studio. It's a very interesting hybrid concept which you do not find many of such examples on the market. That's why investors we're talking to sometimes are confused. So they do not understand how to assess the valuation of our company properly. So we started as a service company, but then we built the product expertise and start to deliver our own products. And right now those two wings of the businesses live together. So we have products, Mailtrap IO, we have Coupler IO and Titan Apps IO, those products are from completely different industries. Mailtrop is from the email sending coupler, AI is the data analytics platform and Titan apps is the set of productivity tools for Atlassian and Monday.com marketplaces and consultancy part which actually we started with very famous for building Calendly for instance, from the very scratch.

[00:01:52] Sergiy Korolov:
Tope is the founder of Calendly. He's our good friend and he speaks about Rails for a lot during his podcasts and interviews and we really appreciate that. So we right now build another successful company or product for the company, Tradezilla. So which is growing just significantly, like heavily, exponentially. And many other companies worked with us, mostly startups, and we help them to grow from zero to millions of dollars in ARR.

[00:02:29] Omer Khan:
Great. So let's focus on Mailtrap. Tell us a little bit more about. You explained this briefly, but what does the product do, who's it for and what's the main problem that you're helping to solve?

[00:02:43] Sergiy Korolov:
So Mailtrap originally was born from the mistake that we've made. We've sent about 20,000 test emails to the customers from the staging environment into production, into production value to the real customers. So it was the huge fuck up. I don't know if you can use such words during the podcast, but yeah, customers were angry and they didn't understand what happened. Kind of it was a set of emails related to some billing. So were they charged or they were not charged? You know, so that's a lot of confusion was brought. And so we decided that we need to build some simple tool that will block SMTP traffic from the staging environments, from the local environments and guarantee by that that the emails will not reach real customers. So that's how Mailtrap was born.

[00:03:44] Sergiy Korolov:
It was 2011, I guess, maybe even earlier. We've never considered that product as the product back then. It was rather just tool that we give back to the community. So we are developers ourselves. Myself, like I'm developer, Yaroslav is developer, our company management team is our developers. And the whole culture of the company was driven by developers and still driven by developers. But back then we were much more integrated into the Ruby on Rails community. We participated in different conferences, kind of speaking on those conferences, making some open source projects which are still a part of the Rails Rails.

[00:04:39] Sergiy Korolov:
Open source. Open source, yeah. And community find out that Mailtrop is not only useful for us, like for elsewhere, but they start to use it. So we made it public. It was very small tool, not a lot of features, but we made it public and community decided that it's pretty useful and start to promote it themselves. So we had zero marketing. It's a perfect example when you find your market fit and I must say that this is very, very complicated to find such market feed. So it's a combination of your, of the concept eat your own dog food.

[00:05:20] Sergiy Korolov:
Right. When you do something for yourself, it works good for you and then it might work well for your community as well. So in this specific case it worked out pretty good.

[00:05:30] Omer Khan:
Yeah. So initially this was an internal tool. You made it available to the community, putting on stack overflow and places like that one. Like, I mean it's grown from like just this internal tool that was never supposed to be a business to a seven figure ARR SaaS. And now you have spun that off and you have a dedicated team focus on mailtrap. I'm curious, how do you spend your time? Like it sounds like you have a lot of plates to juggle here with Railsware and that side of the business and everything you're doing with mailtrap and the other products.

[00:06:11] Sergiy Korolov:
Yeah, true. So I must say that we have a fantastic team. Right now it's about 40 people, all the different roles, product managers, designers, engineers, support marketing people, deliverability experts. So because right now Mailtrop is not only a sandbox, but It's a email delivery platform. So we cover both staging and production already. And this is the. We will talk about challenges later. I guess so of this transition.

[00:06:47] Sergiy Korolov:
But speaking about myself and how do I spend my time, I would say that about 70% of my time I spent on Mailtrap on the role CEO helping team basically with the vision delivery, with the strategizing part, helping them with unblocking any kind of problems that might appear. And this is the major role of CEO, right. You need to make your team productive. So you should see where are the weak points. You need to strengthen them kind of. You need to find proper team players. So it's. We love this concept of Moneyball we talk about.

[00:07:35] Sergiy Korolov:
So if you have seen this movie, if not, I heavily recommend that sometimes you don't need like a team of stars, but you need the team which become a star based on their specifics kind of software. Software soft skills and hard skills. So that's my main goal is to build this team of like star team, not team of stars.

[00:07:59] Omer Khan:
So the 40 people are just focused on Mail Trap only?

[00:08:03] Sergiy Korolov:
Yes, yes, yes. Mailtrap only. And so we have about same size coupler team. We have much smaller team on Titan Ops and we have the rest of the team help like we have other joint ventures products. But this is something we can talk probably in the next episodes. Yeah. And we have this consultancy part which we started with originally as the company.

[00:08:29] Omer Khan:
Great. So Mailtrap is this internal tool. You share it with the community, it starts to take off. People are using this. But for many years it was just a free tool. You didn't monetize it. What happened that shifted your thinking and got you thinking about monetization for mailtrap.

[00:08:53] Sergiy Korolov:
So yeah, as I said, it was a side project for us. Side meaning that we haven't focused on it at all. We were focusing on the other parts of the business. And for about five years this product, or I would call it rather tool, was available online. It was living its own life. We had part time product manager, part time engineer who was working on this product, just adding smaller things here and there. And community loved it kind of more and more customers joined our user community. We had User Voice back then as the tool to collect proposition of the features that customers would like to have.

[00:09:44] Sergiy Korolov:
And we've started to see that there are more and more and more requests like this and this and this. And so we decided, well, you know, maybe it makes sense to make it not just a tool but convert it into the product, start to purchase at least a bit to cover our development effort and the infrastructure costs. And so decision has been made. Five years after being tool Mailtrap has been converted to a product. We've introduced some plans which I don't fully remember. What was the original price? Like 10 bucks or something. And 25. We limited the amount of emails that you can send to the sandbox and a few limitations on the features.

[00:10:33] Sergiy Korolov:
But kind of the strategy, the pricing strategy was pretty simple.

[00:10:37] Omer Khan:
One, how big was the user base when you started looking at pricing?

[00:10:41] Sergiy Korolov:
So it was already back then about 200,000 users. I mean signups. So none of them were active. But I guess back then it was like 20, 25,000 active users. And so right now we have about 100,000 active users.

[00:11:00] Omer Khan:
A lot of founders would probably just say we wouldn't want to monetize it. Let's look at what competitors are doing and let's introduce a paid plan. You took a much more of a data driven approach and you actually interviewed users and ran surveys to figure out your pricing 1. Why did you decide to sort of do it the hard way and what did you learn?

[00:11:23] Sergiy Korolov:
Yeah, so it's a good question. So the first pricing we've introduced, it was pretty simple and without communicating with the customers and without analyzing their behaviors. It's. It was just the first test, I would say. But later then we started to put more and more efforts and we decided, all right, maybe it's time to reconsider the pricing model. We analyzed the behavior of our users from which perspective? So we have product analytics and this is something that I heavily recommend for every product owner to have Product analytics track how like the usage of your product, see what features are used, which are not used, find correlation between feature sets that are used and conversion to the, to the purchase. So that's very important because we have a lot of assumptions kind of we as owners, we think that oh, this feature is so cool. It's like when we will deliver it, users will love it and they will, they will purchase our product 10 times more.

[00:12:34] Sergiy Korolov:
But then you deliver and you don't see any change in this, in the purchase yet. So that's. We have assumptions, right, but then you need to measure the results of those assumptions. And so when you take data from the product analytics and then you take the survey results and as you've mentioned correctly with top to our customers. So we've picked different groups, like more advanced users, less advanced users from the smaller companies, from the bigger corporations, individual users. And we talk to them more than 100 interviews, collecting their feedback about their user flow, how they use product, what they use cases. And so based on these and product analytics, we've already organized the new pricing model. And not only this, but also it helped us to shape the roadmap and prioritize the features that we want to deliver to the users.

[00:13:40] Omer Khan:
Was there any one sort of surprising thing that you learned from going through this process compared to your sort of initial attempt at just guessing at the pricing?

[00:13:52] Sergiy Korolov:
Surprising was not that part, but the other part. We had an assumption then if we will clean up the user experience in the beginning, like first time experience, will be very slick without many clicks and then kind of you just sign up and arrive to the email like the, to your newly created sandbox with all the instructions and the first and just one click to send the email that it will increase the conversion dramatically. But in fact it didn't. So the major finding was that if there is a value, like core value in the product, even if you have 2 more clicks or 20 more clicks to be done to achieve that value, users tend to make those clicks if they understand that value, like they will reach the value after those 20 clicks. So that was a big surprise. I mean there was some change, but it was like a few percent. So it wasn't like 20% change or like 30%, just hardly noticeable I would say. So that was a surprise.

[00:15:10] Omer Khan:
So most of the growth you've implemented, the pricing you've had users participate in helping you figure this out, most of the growth has been coming from organic word of mouth. You know, we talked about that obviously people talking about in the community where you had been very active anyway and then presumably just having a free tier was probably a good viral driver anyway. When you think about getting to that first million in arrangement, was there anything else that helped you get there faster or were those the sort of the, the main sort of growth strategies?

[00:15:54] Sergiy Korolov:
Yeah, word of mouth and community, they drove us to the brand exposure and they built this foundation for our community of the users. But then in certain moment we were on plateau and so at that moment we decided that okay, maybe it's time to invest into marketing. So we found we have hired a few people who helped us because we didn't have anything like there was just a homepage and then sign up and then sign in and so there is an application. So we didn't have blog, we didn't have, so we had some very simple documentation. So and we were absolutely inactive in social media and this is something that we focused on and it had very positive influence actually. So we start to create blog share a lot of use cases. We start to talk more about mailtrap on the different podcast shows like here we talk right now and yeah, and it helped us to start to grow exponentially comparing to what we've seen before.

[00:17:12] Omer Khan:
So I think it was around 2020 that you hit the first million in ARR. Is that about right?

[00:17:19] Sergiy Korolov:
Yeah, I guess around 2020, yeah.

[00:17:22] Omer Khan:
Okay, great. Let's go back to the surveys because I think that's super interesting that you were using surveys to get feedback from users on pricing, but then you also implemented surveys as part of the signup process. But you went one step further and you made this a required thing that people had to do. And you and I were talking about this earlier that there's always this worry that this is going to hurt conversion rates. So just tell me about that. Why did you do that and why was it so important for you to make this a required thing that everybody had to complete as part of sign up?

[00:17:59] Sergiy Korolov:
Yeah, this is one of the best insights I've gotten for the last couple of years. So I guess it's important to mention here to our listeners that Meltrop had this huge transition from just being a sandbox. Actually in 2020 we decided that it's time to not only test emails, but also send and become a competitor to services like SendGrid, Mailgun, Postmark. And our our goal was to build the whole flow for the emails during the development cycle. So you want to test your emails on the staging environment. You have sandbox, you go into production. So you have mailtrap sending email API product which you use to send those emails in production. And so when we've built that part a few years ago, we start to polish first time experience and which I've mentioned before.

[00:19:02] Sergiy Korolov:
And when we see that making it very sleek and without any clicks hasn't changed much, we thought maybe if we will add a few more useful steps for us useful it will not influence conversion as well. And it actually hasn't influenced conversion, but it gave us a huge kind of insight. So we've introduced required survey. We didn't want to overload with like our customers with a lot of questions. So it's important that survey is clickable. So without open questions because people like users do not like to those open questions. So we asked about the intention. If it's a business intention, it's just, just surfing, looking at the product or it's an educational project or it's a pet project.

[00:20:00] Sergiy Korolov:
We asked for the position, like, is it a C level, is it developer, is it marketing person? We asked for the marketing channel because it's very hard to attribute specifically. Sometimes you can attribute, but in many cases you cannot attribute the marketing channel exactly. So user usually can see you on YouTube, then go to Facebook and see some ads and then search in the Internet and like how would you attribute. But when you ask a person, they usually can tell you the most, the, the one that they have noticed and understood. Okay, so this is Mailtrap. I will go and try to work with it. Yeah, and we introduced that. And again, it's something that I recommend to every, to every founder, to every head of product or product lead that I'm talking to from our friends and partners networks.

[00:21:10] Sergiy Korolov:
So it's amazing. Kind of right now we have dashboards where you can say, all right, show me conversion from United States pet projects. And it shows you some very, very little. And then okay, show me like let's say United States and business intention. And then it shows completely different conversion. But if you do not have such opportunity of filtering, then you see, all right, I have like hundreds of thousands of kind of signups over some time and why my conversions are not that great, so what should I fix? And then when you have such filters, you can go to your marketing team and say, you know what, you bring a lot of traffic, that's great. But you bring a lot of folks who are doing pet projects and they do not convert into the paid product. So they do not pay.

[00:22:11] Sergiy Korolov:
So here is the cohort that you should focus on and you show them specific cohort. So it should be like C level business intention and like some tiers of the countries which tend to convert. And that's it. So because those huge numbers in traffic usually can make you blind, kind of you think, what should. What, like what do I do wrong? Like there are hundreds of thousands of users, so why my growth isn't that fantastic, as I would expect? So. It puts you in control of what you're doing and what is the outcome. So that's very important.

[00:22:55] Omer Khan:
You were telling me you were getting about 30,000 signups monthly at one point and you implemented this required survey. And how did that affect the number of people signing up?

[00:23:07] Sergiy Korolov:
Nothing has changed. So that was the insight. So we made it required, I would even say by mistake. So we consider it like making it required, non required. But then, okay, let's deliver it without requirement. But then we'll see if there's going to be some drop. We will introduce this just recommended survey rather than required. But we observed and nothing has changed.

[00:23:40] Sergiy Korolov:
So conversion from sign up to activation stayed the same. So nothing has changed. But we had a lot of benefits after that. Again, we made it very nicely looking this survey. It's just three steps, just a few questions. You click, you choose. So it should be the proper balance. Of course, if you will overload with the questions and click kind of you will introduce complexity then it may influence.

[00:24:08] Sergiy Korolov:
But we made it very clean, very sleek, kind of few questions. And yeah, it is also important when you do surveys, you should randomize the answers kind of. If you have some choices from 1 to 10, like let's say role C level developer marketer, they should change their position for different users. So it should be a random position, otherwise they're going to be a bias. So people will tend to click first one for instance and you will have unfair advantage of the first role and you will have impression, wrong impression that you have C level users. But actually it's going to be a regular user who just clicked first answer. But when you randomize them, there are still users who just blindly click. But if you randomize, so this percentage is distributed among the all answers and so it does not influence the result if you have kind of thousands of customers.

[00:25:13] Omer Khan:
So what's the ultimate objective of this survey? To identify customers, cohorts and intentions within those cohorts to be able to make better decisions. So this helped you make better product decisions, this helped you give better feedback to marketing about where they should focus and ultimately gave you more clarity on who your ICP was.

[00:25:37] Sergiy Korolov:
Exactly. And speaking about surveys, we practice surveys much more than just this. So at some point we decided maybe. So we introduced this transactional emails. So there was a sandbox. Then we introduced transactional emails for production. And then some of our customers start to ask if we didn't provide the email campaign functionality. And they've clearly stated that hey, we don't want to purchase mailtrap for transactional and sandbox, but then for campaigns purchasing other product, we would rather go and purchase one product with all this functionality.

[00:26:19] Sergiy Korolov:
And it pushed us to consider earlier than we expected that maybe we will need to deliver the campaigns or promo emails faster. So instead of. So that was an assumption, right? And instead of building it right away, we've just introduced email campaigns menu item on the left, so the main menu and we put the email campaign there and when you click it, it was just a type form which we clearly said, hey, we are planning to build this functionality, can you help us with some Insights, what would you like to see in this product? And again, for me, it was such a surprise that during a few weeks we've received 300 replies. Like 300 people decided that their feedback is valuable. Like no. No Amazon codes, no, you know, no rewards, no. No discounts, nothing. We just put it into that soon.

[00:27:23] Sergiy Korolov:
We put this email campaign, email marketing soon, and then survey and again, a lot of insights prioritization from the feature perspective. So you don't need to have clashes in your product team. What should go first? And you have already pretty valuable insight on the prioritization.

[00:27:47] Omer Khan:
So I love that. I think that's great. Really smart way of figuring out whether you should go and build that feature and how best to build it. One thing that strikes me is that up until that point, you had a very clear niche with what Mailtrap was doing, because you were really about testing. And that's what you had been built the brand around. And now you're going into the space of sending, which, you know, not only are you potentially competing with these, these other products that you never had to worry about before, but what were, what were some of the, the main challenges you faced when you decided to, to move into the sending space as well?

[00:28:30] Sergiy Korolov:
Yeah. So I must say that there are challenges on top of the challenges and on top of the challenges. So it's definitely not easy. So let me say that one thing, build a fake SMTP where you receive emails. The other thing, building SMTP that sends emails, like the whole Internet wants to hack you and send spam and scam. Like once you declare that you send emails, that's it. Like you constantly have attacks after attacks. It's completely different perspective.

[00:29:03] Sergiy Korolov:
So you need to build spam shield and invest into that a lot. But we will talk about technical challenges later. So the biggest challenge that we are facing right now, and we put a lot of efforts actually to change this perception, is the brand perception. Because before Mailtrap was about not sending email to the inbox of real customers. And it was a message like the core message of the product. But when we start to send emails to customers, so that's the goal for. So there are two opposite goals. For testing email, you must guarantee that it will not send email to the inbox of the real customer.

[00:29:53] Sergiy Korolov:
With the sending product, you. You should guarantee that you will send two inbox. So it's confusing. I mean, we understand it's confusing, but once you think about it as a developer, that there is one tool which covers your development flow. So you start your product and you introduce Mailtrop from the very first test, like we need to sign up on, like forgot password, whatever. So Mailtrop goes into the game early stage and you use it on staging environment. But then when you go to production, there are not many changes. So you have just a configuration for production.

[00:30:37] Sergiy Korolov:
So there are two configurations, staging and production. And Mailtrop does the job. So it guarantees to you that it will never send email from the sandbox from the staging. And it guarantees you that it will send to production. Like from production, it will send to the real user. And that's the biggest challenge that we are facing. Because brand was perceived for so many years by developers like millions of. Because at the current moment we have just about 2 million signups over the course.

[00:31:16] Sergiy Korolov:
So all those users, well, not all of them because last year they're ascending also. But let's say more than a million users considered Mailtrap only as a testing tool. And it takes us efforts to convince them that it's not only testing tool anymore. So it's our major bet right now on sending because it's much more complicated, it's a huge market. And this is by the way, why we decided to move into that. Because although customers loved our product, light testing product, it's a very niche product with a lot of, let's say, alternatives. And those alternatives can be free kind of. It's.

[00:32:10] Sergiy Korolov:
They're not that convenient, but users can decide that, all right, it may not be that convenient, but I will use like free version of some tool. While if we talk about sending, there is no free alternative. We have free package like 3, 3.5 thousand emails you can send monthly for free. But if you need to send more, then it's already paid.

[00:32:41] Omer Khan:
Got it. So again, very interesting that you got user feedback on whether you should build this product, this feature, how you should build it, but you also got insights into what they didn't like about some of the competitors. Right. Can you, can you share an example of that?

[00:33:04] Sergiy Korolov:
So when we were thinking about this sending development, there was a trigger for ourselves to move into the direction because we also. So we were using other famous tool for sending ourselves and we faced a lot of unpleasant things. So we had the problem with deliverability to Office 365, but we never knew about it because all the dashboards inside the service that show that everything is green and nice and kind of no problems, while we've received quite a lot of feedback in the support that I cannot receive my email, I cannot receive my confirmation or like link or Something and so we started investigation and it was close to impossible to find through the provided dashboards and the analytics within the product kind of those other service product. So what are the problems? So what we've did is we've took all the data from that service, put it into the BigQuery and our data analytics team, they set about two, three days digging into this data like gigabytes of data and trying to understand what can be wrong. And so we find out the perspective how you should look at the sending data. And we've built a bunch of interesting dashboards that gives you an experience of drill down reports. So like you have a helicopter view and it shows you, highlights you if there are some risks or there are issues. And if you want to go into the issues you kind of click deeper and deeper and deeper and you can find the root cause of the problem.

[00:35:10] Sergiy Korolov:
And so we've seen that it's so much better experience than we've, we have in that service that we use ourselves, that we start to think well maybe if we will build the product within such functionality it will be very helpful for the other users. And so we start to talk to our community of testing users because of course they evidently they send, if they test sending emails, that they send emails in production. So we've picked different cohorts, kind of smaller customers, bigger customers, individuals, corporations, and we talk to them about their experience with sending, kind of how do they like things, what they didn't like. And we find out that many of them are frustrated about the quality of support, lack of advices from the product. So product does not advise you to what you should do next and kind of how you should do it correctly. There are some hints in documentation, but product doesn't guide you. And we've built sending in a way that product guides you to apply the best approaches. So you have high deliverability, so you have good analytics and we honestly show you if there are some issues and how to fix them.

[00:36:37] Omer Khan:
One sort of semi technical question for you about AI and we've seen recently people getting very excited about vibe coding and being able to build products more easily.

[00:36:50] Sergiy Korolov:
Yeah, that's my favorite topic.

[00:36:52] Omer Khan:
Yeah. And often you find that the honeymoon period ends pretty quickly when they realize that they got, you know, they got sort of a scaffolding, a basic product built but, but when they try to get more complexity into it, it often becomes a nightmare. And I'm curious about how you think about AI, how you use it as part of your business and what's your sort of the direction that you guys are going towards with that.

[00:37:23] Sergiy Korolov:
The thing with AI hype is that there is a lot of hype, but there is also a rational part of it. And with having all this experience of years and years of building software, we try to kind of assess tools properly. Right. So without over expectations or under expectations, just clearly. So you have a test, you can write this code yourself or you can write it with help of Courser. And so you kind of compare the result. So kind of shortly, we use AI inside of the team, but not for wipe. Like Wipe coding can appear for product managers trying to hack something quickly to show before they did it in figma.

[00:38:18] Sergiy Korolov:
So in Figma they just make some screens and then make a prototype, clickable prototype. Right now they can do it with wipe coding, but still sometimes it's still easier to make in clickable prototype in figma. Anyway, so this part of wipe coding here. But we use AI as I'm talking about software, right? Because not software. AI's applicability is very high. So like creating content kind of it should be done smartly, but kind of definitely it is in use. We use for kind of PG decks and presentations and other things, of course. But if we talk about code, then Corso Copilot, we experiment with those tools, our developers are free to choose between those tools.

[00:39:16] Sergiy Korolov:
What we usually do is we have many different. So as a product studio, we have this advantage that different products have different stacks and different, I would say trajectory. So there are simpler products, more complicated products. And so you are able to compare applicability of this technology, AI technology in the different conditions. And what we do is that our engineers, they actually work with Coursever Copilot. So they make some reports and then share in the. We have this craft engineering, craft guild when they share some presentations, when they say that. All right, so it's pretty good for writing tests.

[00:40:12] Sergiy Korolov:
It's great for complicated refactoring when you need to replace some name of the function everywhere. And it should be done so kind of swiftly. It's good in kind of templatization or it's good in creating first version of UI from the Figma screenshot. So kind of different team members use those tools, they share feedback. And so what we see right now, at least at this specific moment. So it's September 24, 2025, AI is just a tool that helps good engineers to be productive. It definitely fantastic in helping working with documentation, with analyzing code. So when you need to dig some logic out of the code base, it's so much Easier because AI is able to combine knowledge from the code base with the technological documentation and propose you some solution which you may accept or you may choose something different, but it just reduces the amount of time you spend on educating yourself about this context.

[00:41:41] Sergiy Korolov:
So yeah, this wipe code is the thing that and we just had a call before this podcast recording with my team for launching campaign Railsware web services. So like it's just a development of software like I mentioned before and one of our campaigns going to be we will rewrite your wipe code. So because it really becomes a nightmare as you've mentioned and we already have three clients who came to us with the wipe coded projects. But that's fine. I mean like it's just, it's just changing paradigma how you started the product before you usually need to have some pro engineer, certain level of engineer who can quickly build proof of concept or MVP with Ruby on Rails or Symfony or any or like Django frameworks and then you go to investors. Right now this cycle is shortener shortened so you, you can wipe code something proof that this feature or idea can work, get round of investments and then come to company like Railsware or other company with strong engineers who can create a good product from that concept. So but usually you should throw away the code that is written. It's hardly maintainable so you will need to spend more time to maintain it rather than rewrite things from scratch.

[00:43:24] Omer Khan:
Yeah, I mean I've had this conversation a lot with founders in my SaaS Club community and I think where we've sort of ended up is you know, it's if you're, if you're non technical or even if you're technical using this sort of vibe coding sort of approach to take an idea to prototype maybe an mvp. Whether you're going towards investors or trying to get those first five or 10 customers, you can probably get that far. But if you think that you can continue that to get to a seven figure Arsas business and beyond, that's probably highly unlikely. At least based on where we are today.

[00:44:05] Sergiy Korolov:
Highly unlikely. Yeah. Unless it's I don't know, it's like database of vacancies and you're in a spot like you have some very good traffic source which goes I know candidates and firms. So when you have some sweet spot in marketplace and you just build some simple version of marketplace, very, very simple one and then you can make those figures but just a few more features here, a few more features there and it stops working. So it's hardly maintainable.

[00:44:36] Omer Khan:
Yeah. So there definitely comes a time where this thing that you've built, it needs a professional developer to take over and continue. And I think especially if you're working with a developer who uses AI but knows how to implement the right guardrails in place to be able to use it for what it's good at, but not give it any more leeway to do more than you need to, I think that is a superpower combination. And so I think that that's a really interesting space that's coming out. And the more I see developers who people are like, oh, this is going to put developers out of jobs, I think it's actually going to be the opposite. And especially when you have developers who are really smart with how they use AI, I think that's going to be a killer combination.

[00:45:26] Sergiy Korolov:
Just one quick comment here speaking about that. We've seen it as the another tool that makes you like mix developer a bit more productive for some percentage. Hard to say which percentage because it really depends on the complexity of the product, kind of skill of the engineer and so on. But definitely it's not like a replacement of engineers. And it's not 300% boost, it's just, I don't know, 20, 30, 50% boost. But if you will roll back kind of history, you will see that such changes happened before. So there was assembler or before assembler, there were like those paper cards and then there was assembler. It was so much more productive than those paper cards.

[00:46:15] Sergiy Korolov:
But then languages like Turbo Pascal appeared and it became like engineers become 100 times more productive than they were with assembler. But then rapid development frameworks appeared like Delphi. And so developers were able to build desktop applications with the speed they haven't seen before. And like much smaller teams. Similar things happened with the web when frameworks like Ruby on Rails appeared on the market. Kind of just compare how much software engineer was able to build with those open source solutions. It's just they became hundred times more productive. So that was much more influential point in the productivity of software developers than right now AI.

[00:47:12] Sergiy Korolov:
But I'm saying again this is for this moment, I believe that it will be hard to achieve with LLMs, kind of some bigger results, much bigger results. But if they deliver like those giants will develop some other logic of this generative AI which will think like a person, then it can be a trouble. But so far LLMs, they do not give you such boost like it is promoted. So I think it's a bit overhyped at the moment.

[00:47:45] Omer Khan:
Yeah. All right, let's get onto the lightning round. I have got seven quickfire questions for you. Are you ready?

[00:47:52] Sergiy Korolov:
Yep.

[00:47:53] Omer Khan:
Okay. What's one of the best pieces of business advice you've received?

[00:47:58] Sergiy Korolov:
Go with the flow.

[00:47:59] Omer Khan:
What book would you recommend to our audience and why?

[00:48:03] Sergiy Korolov:
I would recommend the Power of Now by Egghartole. So it's not about business, but it's about the possibility to appreciate the moment Now. So when you are in active development of the business, you are overstressed and you need some point where you can appreciate the moment of now and the work you do. Do not wait until you become a billionaire, and only then you will appreciate yourself. So that book teaches you to appreciate the Moment Now.

[00:48:40] Omer Khan:
That's a great book. I'm definitely somebody who overthinks, and I read that book many years ago. And whenever my wife sees my overthinking, she's always like, you need to go back and read the Power of Now.

[00:48:55] Sergiy Korolov:
Yeah, that's fantastic. And there is one more of the same author is the New Earth. It's even better, I would say. But you need to read it after the Power of Now.

[00:49:08] Omer Khan:
Cool. What's one attribute or characteristic in your mind of a successful founder?

[00:49:14] Sergiy Korolov:
So you never stop?

[00:49:16] Omer Khan:
That's a good one. What's your favorite personal productivity tool or habit?

[00:49:21] Sergiy Korolov:
My productivity, it's Spotlight. Like I like this experience in every tool when there is a search line and you work through search line or terminal command line. So it's. And that's why I like kind of this new ChatGPT experience. I mean this GPT AI experience. This. It's like an advanced command line, actually. So you type what you want and you get the answers.

[00:49:50] Omer Khan:
What's a crazy or biz new or crazy business idea you'd love to pursue if you had the time? Not that you already have a number of businesses you're working on.

[00:50:01] Sergiy Korolov:
Oh, Jesus. No, I don't have anything in my mind honestly here.

[00:50:06] Omer Khan:
I think you got to pass on that given all the products that you're. You're building anyway.

[00:50:10] Sergiy Korolov:
Yeah. Yeah. So we just, for those who don't know, we have really multiple products in development. Yes. And the portfolio kind of. Which is not. Has not been released or even started, is even bigger. So I'm rather searching where to stop, not just what to add in this portfolio.

[00:50:31] Omer Khan:
What's an interesting or fun fact about you that most people don't know?

[00:50:35] Sergiy Korolov:
I am a professional swimmer.

[00:50:37] Omer Khan:
Okay.

[00:50:39] Sergiy Korolov:
Well, was in my kind of early years. Yeah. Of course, I'm not a professional swimmer anymore. Like I'm too old, but I was a part of Olympic reserve in my country.

[00:50:51] Omer Khan:
Nice. Nice. And finally, what's one of your most important passions outside of your work?

[00:50:57] Sergiy Korolov:
Sports activity. I do snowboarding in winter. I do bike and running in summer and spring. I do swim sometimes, but I had enough of my of swimming in my early days. Yeah. So that's. And I do love spending my time with family. So all my family trying to be as active as I am.

[00:51:23] Sergiy Korolov:
So we love to spend time on the ski slope and riding bikes.

[00:51:30] Omer Khan:
Great. Well, Sergey, thank you so much for joining me. It's been a pleasure. If people want to check out Railsware, they can go to railsware.com and if people want to check out Mailtrap, it's Mailtrap IO. And if folks want to get in touch with you, what's the best way for them to do that?

[00:51:48] Sergiy Korolov:
Just write at contact or find me on LinkedIn.

[00:51:54] Omer Khan:
Great. Well, thanks again. Thank you for unpacking your story and sharing some really super practical insights and lessons about your experience with building Mailtrap. And I wish you and the team the best of success.

[00:52:09] Sergiy Korolov:
Thank you very much. Thank you for invitation and it was pleasure to talk to you.

[00:52:13] Omer Khan:
Awesome. Cheers.

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