Companies Using Mailgun

With 10+ years in web crawling and technographic data analysis, I've examined Mailgun's growth trajectory and customer profile using our 185,768 enriched company dataset (a 64.9% match rate against detected domains), as of our August 2026 crawl at TechnologyChecker.io. We matched Mailgun domains against LinkedIn company profiles to uncover who actually uses this transactional email API, where they're located, and how migration patterns are shifting across the competitive set.

Growth Trajectory

Mailgun's crawl data starts at 107 active domains in March 2013, just three years after its founding and one year after its Y Combinator batch. Growth was steady through 2017 (19,930 active domains by December), then accelerated sharply. By January 2020, active domains had nearly doubled to 37,737. The historical series hit 168,693 active domains in May 2025 before pulling back to 148,607 by July 2025, a 12% decline in two months.

That pullback looks like post-spike normalization: Mailgun discontinued its original free plan in 2020, and the Sinch acquisition in 2021 brought organizational changes. We now detect Mailgun on 286,138 domains and the count is essentially flat month over month (284,272 in July 2026, 286,138 in August). The two figures are not like-for-like, because the set of domains we crawl turns over every month, with dead sites dropping out and newly discovered ones added, and our detection signals widen over time, so treat the step across the chart's 2025-to-2026 gap as coverage rather than growth.

"The 12% pullback from Mailgun's May 2025 peak didn't signal collapse. It looked like post-spike normalization after the unusual jump from 106,346 to 134,503 domains between April and May 2024, and a year later the platform is the fourth most detected sender on the web and flat month to month." - Mehmet Suleyman, CEO at TechnologyChecker.io

Sales Signal: 5,357 domains have dropped Mailgun since we began tracking it in March 2026. That is the pool currently in motion, and the smallest churn figure of any major sender in this category.

Customer Profile

55.6% of Mailgun customers have 1-10 employees, and 82.8% have fewer than 50. Small dev shops, SaaS startups, and freelancers are the core. But the top 50 list paints a different picture: Ford, Uber, Salesforce, GE Aerospace, Pizza Hut, Taco Bell, and AstraZeneca are all there, and 36 of the 50 have 10,001+ employees. These enterprises use Mailgun on specific subdomains: Ford on warriorsinpink.ford.com, Salesforce on trailhead.salesforce.com, Kuehne + Nagel on jobs.kuehne-nagel.com. They aren't running company-wide email on Mailgun. They're using it for isolated transactional workflows.

Sales Signal: Enterprise presence is real but narrow. Target the specific team running the subdomain, not central IT. The buying decision was made by a developer, not a CTO.

Industry and Geographic Concentration

Retail leads at 4.6% of enriched companies, followed by IT Services and IT Consulting (4.42%) and Software Development (4.36%). No industry exceeds 5%. That's one of the flattest industry distributions in our database, and it makes sense for a horizontal infrastructure tool. Developers in every vertical need transactional email.

Geographically, the US dominates at 41.5% (73,561 companies). The UK is second at 11.4%, Australia at 5.9%, and Canada at 5.1%. English-speaking markets total roughly 64% of the enriched base. The Netherlands (8,822 companies, 5.0%) punches above its weight, likely reflecting the country's dense SaaS ecosystem. 39.4% of Mailgun customers were founded in the 2010s, confirming that digital-native companies are its core demographic.

Sales Signal: Vertical-specific messaging won't work here. Lead with developer productivity and API reliability. The Netherlands and Germany offer less-saturated markets where Mailgun adoption is already strong.

Migration Patterns

Migration here counts domains we watched switch since March 2026, so the numbers are small by design and current by construction. Mailgun is net positive overall, and the wins come from the campaign builders: 814 domains arrived from MailChimp against 180 leaving, and 479 from Klaviyo against 321 leaving. That is a developer adding transactional sending, not a marketing team switching platforms.

The losses are on the API side. 187 domains went to SendGrid against 119 arriving, a net loss of 68, and 182 went to Amazon SES against 69 arriving, a net loss of 113. The Amazon SES pattern aligns directly with G2's top complaint about expensive pricing. Amazon SES charges $0.10 per 1,000 emails with no monthly fee. For high-volume senders, that's dramatically cheaper than Mailgun's tiered plans.

Worth noting the counter-example: Omnisend's public case study describes switching FROM Amazon SES TO Mailgun, citing 99% delivery rates. Companies prioritizing deliverability over cost still choose Mailgun.

"The net loss to Amazon SES isn't a quality signal, it's a price signal. Amazon SES offers raw SMTP at rock-bottom rates, and high-volume senders who don't need Mailgun's developer tooling are making a rational cost decision. The question for Mailgun is whether its API experience justifies the premium for the majority of its base that is under ten people." - Mehmet Suleyman, CEO at TechnologyChecker.io

Sales Signal: Companies moving to Amazon SES are price-sensitive and volume-heavy. Target them with tools that make SES easier to manage. Companies arriving from MailChimp and Klaviyo are adding transactional email to an existing marketing stack and need integration help.

Technology Ecosystem

The tech stack overlap reveals what a typical Mailgun customer's site looks like. Google Analytics sits on 60.01% of Mailgun domains and Cloudflare Browser Insights on 11.19%. WordPress leads the CMS side at 32.47%, with Squarespace second at 4.72%, and Shopify appears on 16.77%.

Marketing automation overlap is deliberately thin: HubSpot at 5.25% and HighLevel at 2.35% are the leaders, which means the overwhelming majority of Mailgun domains carry no campaign platform at all alongside it. That is the signature of a pure transactional deployment.

Sales Signal: If your product can bridge transactional and campaign email, the pitch writes itself for the minority running both. For the majority running Mailgun alone, the opening is deliverability and cost monitoring, not consolidation.

G2 Review Signals

Ease of use leads G2 reviews with 23 mentions, followed by reliable delivery (18) and high-volume performance (15). On the negative side, expensive pricing tops complaints at 11 mentions, followed by deliverability issues (8) and steep learning curve (6).

The pricing complaint gained new fuel in December 2025 when Mailgun doubled its Flex (pay-as-you-go) rate from $1 to $2 per 1,000 emails. Companies leaving for Amazon SES ($0.10 per 1,000) are the ones feeling the cost squeeze. The Dribbble case study, where open rates doubled after switching to Mailgun, validates the deliverability strength that G2 reviewers praise. Cinemark's use of Mailgun's validation API to clean email lists shows the platform's value beyond simple sending.

Sales Signal: If your product reduces email volume through better targeting or list hygiene, position it as a cost-reduction tool for Mailgun customers considering Amazon SES purely on price.

Key Takeaways

1. Mailgun is a developer-first transactional email API with genuine Fortune 500 penetration, but enterprise usage is narrow and subdomain-specific, not company-wide infrastructure.

2. The customer base is 55.6% micro-businesses (1-10 employees), with 39.4% founded in the 2010s. Digital-native small businesses are the core market.

3. Industry distribution is remarkably flat. Retail leads at just 4.6%. No vertical exceeds 5%, making Mailgun one of the most horizontal tools in our database.

4. Mailgun wins against the campaign builders and loses to the APIs: net +634 against MailChimp and +158 against Klaviyo, but -68 to SendGrid and -113 to Amazon SES. Price sensitivity drives the Amazon SES outflow.

5. Sinch owns both Mailgun and Mailjet, positioning them at different ends of the same category. G2's top pro (ease of use) and top con (pricing) map cleanly onto migration data: developer-focused companies stay, cost-focused ones leave for Amazon SES.

Sales Applications

Outreach template for Mailgun customers:

"Hi [Name], I saw [Company] uses Mailgun. Our data shows 83% of Mailgun's base are teams under 50. If email costs are growing faster than your sending needs justify, [specific value prop]. Are you evaluating your email stack this quarter?"

Targeting strategy: Filter by company size (1-50 employees), industry (IT Services or Software Development), geography (US or UK). Layer on tech stack to find the minority running HubSpot or HighLevel alongside Mailgun, since they're maintaining separate stacks and may want consolidation.

Competitive angle: Price-sensitive senders go to Amazon SES. Feature-seeking companies go to SendGrid. Position based on which path your prospect is considering. Use G2 pricing complaints (11 mentions) as an opener with high-volume senders.

Explore the full Mailgun install base at TechnologyChecker.io: 286,138 active domains with 185,768 enriched companies including industry, size, location, and tech stack data.