Which ESP do top newsletters use? Market data

Which ESP do top newsletters use? Most articles asking that question never actually check. They rank platforms by affiliate payout, dress it up as research, and push you toward whichever tool pays the highest commission. We took a different route. Newsletrix detects the sending platform behind every newsletter it ingests, so instead of guessing, we counted. Across the roughly 9,000 newsletters we track, no single ESP owns the market, and the answer shifts hard depending on who is behind the list.

The short answer: most popular ESPs for newsletters

Mailchimp still sends the largest single slice at about 22%, helped by a long tail of small businesses and side projects that signed up years ago and never left. beehiiv sits at roughly 18% and is climbing faster than anything else in the set. Klaviyo holds around 12%, almost all of it retail and ecommerce. After that the field spreads out: Kit, Substack, MailerLite, Brevo, Salesforce Marketing Cloud, HubSpot, and Iterable each take a single-digit share, and a scatter of smaller and self-hosted setups make up the rest.

If you want it in one sentence: Mailchimp leads newsletters overall, beehiiv leads among independent creators, and Klaviyo leads anything selling a product. One caveat before anyone quotes these as global figures. This is the mix in the newsletters we track, which skews toward English-language publishers that someone thought worth monitoring. The direction is reliable, the second decimal place is not. We refresh the detection on every send we ingest, so the numbers move as the market does.

How we detected the ESP, so you can trust the numbers

Every email carries the marks of the platform that sent it, whether the sender wants it to or not. We read four of them. The DKIM signing domain is the strongest tell, because the cryptographic signature is tied to the platform's own domain and is hard to fake. The Received headers show the path the message took, which usually starts on the ESP's outbound servers. The domain that wraps click-tracking links is another giveaway: Mailchimp routes clicks through list-manage.com, beehiiv and Kit each use their own tracking hosts. The unsubscribe URL is the last one, and it is remarkably consistent within a platform.

Put those four signals together and a single email is enough to name the sender with high confidence. That is also the honest limit of the method. Detection tells you the platform, not the plan, the list size, or whether the team is happy with it. A brand on Salesforce Marketing Cloud might be sending one newsletter a month or four campaigns a day, and the headers look the same either way. We can tell you what they send from. We cannot tell you how well it is going inside their account.

ESP share splits hard by who is sending

The single leaderboard hides the only finding that matters: ESP choice is segmented by type of sender, and the segments barely overlap. Treat the overall table as a starting point, then split it three ways.

Among independent and creator newsletters, beehiiv and Kit dominate, with Substack and Ghost taking the writers who want a built-in subscription wall. This is the segment moving fastest, and it is where beehiiv has already passed Mailchimp in our sample. These publishers want growth tooling, referral mechanics, and an ad network baked in, and they switch platforms readily when a better one shows up. If you only read creator Twitter, you would think beehiiv had won email outright. It has not, because creators are a slice of the market, not the whole of it.

Among small businesses and lean marketing teams, Mailchimp, MailerLite, and Brevo carry most of the volume. This is the inertia segment. A lot of these lists were set up on Mailchimp before beehiiv existed, and a working list that mails twice a month gives nobody a reason to migrate. Retail and enterprise is a different world again: Klaviyo owns ecommerce, Salesforce Marketing Cloud and Iterable handle the large consumer and media senders, and HubSpot picks up B2B marketing teams who want email living next to their CRM. These buyers care about segmentation and revenue attribution far more than about referral widgets, so the creator-favorite tools rarely show up here at all.

The migration we keep seeing: Mailchimp and Substack to beehiiv

One pattern shows up more than any other when we watch senders over time: lists moving off Mailchimp or Substack and onto beehiiv. The Mailchimp exits are usually creators who outgrew a tool built for general marketing and wanted newsletter-native growth features. The Substack exits are usually writers who got tired of paying a 10% cut of subscription revenue and wanted to own their audience outright.

A switch is visible in the headers within one send. The DKIM signing domain changes first, the click-tracking host changes with it, and the unsubscribe URL takes on the new platform's format. Sometimes the sending domain stays the same while everything underneath it flips, which is the clean signature of a migration done well, with the domain authenticated on the new platform before the first send. When we see that combination, a competitor has just changed ESPs, and it usually means they are reinvesting in the channel rather than coasting. That is worth noticing if you compete with them. We cover how to read this kind of change in our guide on detecting a competitor's ESP.

What platform do famous newsletters use

People expect the biggest newsletters to run on whatever tool tops the listicles. They almost never do. The largest media newsletters run on enterprise sending infrastructure built for volume and ad operations, not on the platforms a solo creator picks. Morning Brew and lists at its scale show the marks of systems like Sailthru, Iterable, or custom in-house tooling, chosen because they need fine-grained segmentation and their own ad-serving logic, not because the onboarding was friendly.

So the famous-newsletter question is a trap if you are choosing a tool for yourself. The platform that lets a media company manage a few million addresses and a sales team is the wrong fit for a 5,000-subscriber list, and the reverse is true too. What the giants use tells you where the market goes at scale. It does not tell you what to pick at your size. For the choice most independent publishers really face, our breakdown of Substack vs beehiiv vs Kit is the more useful comparison.

How to check any newsletter's ESP yourself

You can do this by hand. Open a newsletter, view the original or raw source in your mail client, and look for the DKIM signature domain in the header block. Then hover the links and the unsubscribe button and read the domains they point to. Those two signals alone will name most platforms. The catch is that doing it across dozens of competitors, every send, gets old fast, and you lose the history the moment you delete the email. That history is the part worth keeping, because a one-time snapshot misses the migrations.

If you would rather not parse headers, the Newsletrix ESP detector does it for you, and there is a fuller walkthrough of the manual method in our guide on how to find what ESP a company uses. Either way, remember the tradeoff that cuts both directions: the fingerprints you read on a competitor are the same ones they can read on you. Your ESP, your cadence, and your sponsors are all public to anyone willing to subscribe. The only edge is in who bothers to look, which is the whole reason to read competitor newsletters systematically rather than ad hoc. A flat advertiser feed from a tool like MailCharts shows you who is sending without the platform context that explains how, and the platform is often the first sign a competitor is about to change how they play.

Frequently asked questions

What is the most popular ESP for newsletters?

In the newsletters we track, Mailchimp still sends the single largest share at roughly 22%, with beehiiv close behind near 18% and growing faster than anything else in the set. Klaviyo holds around 12% on the back of retail and ecommerce sends. There is no global registry of ESP usage, so any answer is a sample. The honest version is that no single platform owns newsletters, and the leader changes the moment you split the data by who is sending.

How can you tell which ESP a newsletter uses?

You read the email's own fingerprints. The DKIM signing domain, the path in the Received headers, the domain that wraps click-tracking links, and the format of the unsubscribe URL each point at a specific platform. Mailchimp wraps links through list-manage.com, beehiiv signs from beehiiv.com infrastructure, and most platforms leave an unsubscribe pattern that is hard to disguise. One email is usually enough to identify the sender.

Is beehiiv bigger than Mailchimp?

Not yet, by total share in our sample. Mailchimp covers a far wider base of small businesses, nonprofits, and side projects, which keeps its overall count ahead. But among dedicated independent newsletters, beehiiv has already passed Mailchimp, and it is the platform we see receiving the most inbound migrations. On the current trend the two are converging inside the creator segment.

What email platform does Morning Brew use?

Large media newsletters like Morning Brew rarely run on the off-the-shelf tools creators use. Their headers point to enterprise sending infrastructure such as Sailthru, Iterable, or custom in-house systems, chosen for volume, segmentation, and ad operations rather than ease of setup. The practical takeaway is that the biggest newsletters are not a guide to what a smaller publisher should pick.

Can a competitor detect my ESP?

Yes. The same fingerprints we read are visible to anyone who receives one of your emails, including a competitor who subscribes with a research inbox. Your ESP is not a secret you can keep. The useful response is not to hide it, which you cannot, but to know that your own platform, send cadence, and sponsors are equally readable from the outside, and to track competitors the same way.

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