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 95,475 enriched company dataset (a 51.29% match rate against detected domains), as of our March 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 platform hit 168,693 active domains in May 2025, its all-time peak. Since then, it's pulled back to 148,607 by July 2025, a 12% decline in two months.

The recent drop likely reflects post-spike normalization: Mailgun discontinued its original free plan in 2020, and the Sinch acquisition in 2021 brought organizational changes. Still, the 12-year trajectory from 107 to 168,693 domains represents genuine, sustained adoption.

"The 12% pullback from Mailgun's May 2025 peak doesn't signal collapse. It looks more like a post-spike normalization after the unusual jump from 106,346 to 134,503 domains between April and May 2024. The underlying growth trend from 2013 through 2024 remains remarkably consistent." - Mehmet Suleyman, CEO at TechnologyChecker.io

Sales Signal: Mailgun's install base peaked recently. Companies that adopted during the 2024 growth spike are still in buildout mode and open to new tooling.

Customer Profile

69.8% of Mailgun customers have 1-10 employees, and 86.7% have fewer than 50. Small dev shops, SaaS startups, and freelancers are the core. But the top 50 list paints a different picture: Accenture, McDonald's, IBM, PwC, Shell, Uber, Ford, and Pfizer are all there. 48 of the 50 have 10,001+ employees. These enterprises use Mailgun on specific subdomains: McDonald's on email.events.mcdonalds.com, Shell on email.offersbank.shell.com, UPS on email.careers.ups.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

Software Development leads at 5.05% of enriched companies (4,284), followed by Retail (4.45%) and IT Services (4.31%). No industry exceeds 5.05%. 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 42.8% (40,891 companies). The UK is second at 10.2%, Australia at 4.6%, and Canada at 4.2%. English-speaking markets total roughly 57% of the enriched base. The Netherlands (3,359 companies) punches above its weight, likely reflecting the country's dense SaaS ecosystem. 42.67% 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

This is where the data gets sharp. Mailgun is losing ground to both SendGrid and Amazon SES. 2,629 companies left Mailgun for SendGrid vs. 2,249 that came in, a net loss of 380. Against Amazon SES, the gap is wider: 2,304 departed vs. 1,231 gained, a net loss of 1,073. The Amazon SES migration 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.

The Mailjet migration is nearly balanced (720 in, 813 out), which makes sense because both are Sinch-owned products. Against SparkPost, Mailgun holds a net positive of +196. Interestingly, Omnisend's public case study describes switching FROM Amazon SES TO Mailgun, citing 99% delivery rates. That's the opposite of the aggregate trend, which suggests that companies prioritizing deliverability over cost still choose Mailgun.

"The net loss of 1,073 companies 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 69.8% micro-business segment." - 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 moving from SendGrid to Mailgun are prioritizing API quality over price.

Technology Ecosystem

The tech stack overlap reveals what a typical Mailgun customer's site looks like. HighLevel (7.09%) and Klaviyo (6.05%) lead marketing automation overlap, indicating that Mailgun users often run separate systems for transactional and marketing email. Hotjar (9.25%) and Microsoft Clarity (8.81%) are the top analytics tools, both heat-mapping and session-recording products used by product-focused teams.

AngularJS (4.91%) and RequireJS (3.57%) in the JS framework overlap point to mature web applications. Squarespace (4.72%) leading CMS is notable: these aren't WordPress-heavy shops but businesses pairing no-code site builders with a developer-grade email API.

Sales Signal: The HighLevel and Klaviyo overlap confirms that Mailgun users often maintain separate stacks for transactional and marketing email. If your product can bridge that gap, you have a natural pitch: "You're paying for Mailgun AND Klaviyo. We handle both."

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 69.8% micro-businesses (1-10 employees), with 42.67% founded in the 2010s. Digital-native small businesses are the core market.

3. Industry distribution is remarkably flat. Software Development leads at just 5.05%. No vertical exceeds that threshold, making Mailgun one of the most horizontal tools in our database.

4. Mailgun is losing net migration battles to SendGrid (-380) and Amazon SES (-1,073), but gaining from SparkPost (+196). Price sensitivity drives the Amazon SES outflow.

5. Sinch owns both Mailgun and Mailjet, explaining their near-even migration. 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 69.8% of Mailgun's base are small teams. 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 (Software Development or IT Services), geography (US or UK). Layer on tech stack to find companies running HighLevel or Klaviyo 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: 186,000+ detected domains with 95,475 enriched companies including industry, size, location, and tech stack data.