Mailgun
AcquiredYC W11San Francisco, US · 51 employees · 13 known investors
Mailgun provides an API platform that enables businesses to send, receive, and track transactional and marketing email messages.
Also known as MailGun · Mailgun Technologies
Founders & leadership· Y Combinator alumni (W11)
Investors · 13
Also in the syndicate · 8
Company profile
researched Aug 2026Mailgun is an email delivery and deliverability platform that lets companies send, receive, track and optimize transactional and marketing email programmatically. Access is provided through RESTful HTTP APIs and an SMTP relay, with official SDKs for languages including Python, Ruby, PHP, Java, C#, Node.js and Go. Typical use cases described by sources include transactional messages such as receipts, two-factor authentication codes and password resets, as well as marketing and promotional campaigns, plus inbound routing and parsing of incoming messages and connecting email event data to other systems such as CRMs.
The product line is organized into several modules: Send (email sending infrastructure, templates, tracking, analytics and webhooks), Optimize (deliverability tooling including inbox placement, reputation monitoring and deliverability services), Validate (real-time email address validation via API or list upload) and Inspect (pre-send preview and accessibility/rendering quality assurance, described as building on tooling from Email On Acid). The API supports separate US and EU processing regions (api.mailgun.net and api.eu.mailgun.net) so that message data, logs, suppressions, mailing lists and statistics remain region-bound while account and billing data replicate globally, addressing data-residency requirements. Supporting capabilities documented in the API reference include domain and DKIM management, suppression lists (bounces, complaints, unsubscribes), routes and forwards, mailing lists, IP pools and dedicated IP warmup, subaccounts, bounce classification, tags, events, metrics and logs.
Public sources describe a customer base of more than 150,000 businesses, with named customers including Lyft, Microsoft, Dribbble, Wikipedia, NHL, American Express and Substack; other sources also name Slack, GitHub and Reddit. Reported annual send volume varies by source, from over 250 billion emails per year to over 600 billion emails a year.
Founding story
Founded in 2010 by Ev Kontsevoy (Founder/CEO) and Taylor Wakefield, and accepted into Y Combinator's Winter 2011 batch. A third-party profile also lists Alexander Klizhentas among the founders. The premise was to give developers a scalable, reliable way to send large volumes of email with high deliverability without operating their own mail infrastructure. One source instead attributes Mailgun's origin to Rackspace, which conflicts with the Y Combinator and founder records.
Business model
B2B software-as-a-service sold on a usage- and feature-tiered subscription basis, with self-service signup and an enterprise sales motion for high-volume senders.
Recurring monthly subscription plans priced by included email volume and feature set: a Free tier (100 emails/day), Basic from $15/month (10,000 emails/month), Foundation at $35/month (50,000 emails/month) and Scale at $90/month (100,000 emails/month), each with overage pricing per 1,000 additional emails (from $1.80 down to $1.10 depending on plan) and per 100 email validations (from $1.20 down to $0.80). Custom-quoted enterprise agreements add bespoke features, deliverability services and burst-sending SLAs. Optimize and Inspect are priced as separate products, and pricing is offered in USD, EUR and GBP.
Traction
Sources cite more than 150,000 business customers (an earlier Thoma Bravo statement references over 100,000), including 8 of the 10 largest technology companies. Stated volumes range from over 2 billion emails per month and more than 250 billion per year to over 600 billion emails per year. Company-reported customer outcomes include 21% decreased bounces, 65% increased open rates and 100% increased clicks. One third-party profile estimates annual revenue between $6M and $16M and lists 51 employees.
Latest developments
As of the most recent sources, Mailgun markets four product lines (Send, Optimize, Validate and Inspect), with Inspect incorporating quality-assurance tooling associated with Email On Acid, and promotes AI-assisted send-time optimization. API documentation is now hosted under the Sinch brand. In May 2025 Thoma Bravo published a "Behind the Deal" episode with former CEO Will Conway and former CTO Josh Odom reviewing the company's path from Rackspace spin-out to email API provider. A third-party profile lists William Conway as CEO, Tim Keithahn as CFO and Josh Odom as CTO.
▸Full profile — market position, technology, go-to-market, geography, history, risks & controversies
Market position
Positioned as one of the leading providers in the email API/infrastructure category. A Thoma Bravo partner described the space as having roughly three players at the time of diligence — Mailgun, SendGrid (now owned by Twilio) and SparkPost (owned by MessageBird) — and characterized Mailgun as the fastest-growing of the three with the highest margins, while SendGrid was the larger, rapidly growing but unprofitable leader and SparkPost grew more slowly but profitably.
Cited differentiators include an API-first, developer-centric design with multi-language SDKs; scale and reliability across very high send volumes; a combined suite spanning sending, deliverability optimization, address validation and pre-send inspection; selectable US or EU data residency from a single account; and deliverability expertise offered as a service alongside the software.
Technology
Cloud-based sending infrastructure exposed via URI-versioned REST APIs plus SMTP endpoints, returning JSON with RFC-2822 date encoding and standard HTTP status codes, and applying documented rate limiting via X-RateLimit-Limit/Remaining/Reset headers. Separate US and EU stacks handle regional data processing (api.mailgun.net / api.eu.mailgun.net; smtp.mailgun.org / smtp.eu.mailgun.org; mxa/mxb inbound servers; open and click tracking endpoints). Feature-level technology includes authentication protocols (SPF, DKIM, DMARC, BIMI), dedicated IPs and IP pools with automated warmup, bounce classification, suppression management, webhooks and event logging, inbound routing and parsing, template management, send-time optimization and AI-assisted sending tools. Operational hostnames under mailgun.net include api.mailgun.net, api.eu.mailgun.net, smtp.mailgun.net and numerous mail-transfer hosts.
Go-to-market
Product-led, developer-first distribution: free tier and self-service signup, extensive public API documentation, SDKs, knowledge center and a content/research program (for example an email benchmark report based on a survey of 1,200+ senders and analysis of 400 billion emails, and a commissioned Forrester Total Economic Impact study). Higher tiers are supported by sales-assisted motions including demos, quotes, phone and chat support, and regional deliverability experts.
Software developers and engineering teams at businesses that need programmatic email infrastructure, ranging from small senders on free and low-cost tiers to high-volume enterprise senders; cited customers include Lyft, Microsoft, Dribbble, Wikipedia, NHL, American Express, Substack, Slack, GitHub and Reddit.
Geography
Headquartered in San Antonio, Texas with remote teams in San Francisco and Austin according to the Y Combinator profile; other directories list San Francisco, California as headquarters. Service infrastructure is hosted in both US and EU regions, with localized support and regional deliverability specialists.
History
Founded 2010; participated in Y Combinator (Winter 2011) and raised seed capital in 2011. Acquired by Rackspace in 2012, where co-founder Taylor Wakefield subsequently spent three years as a product director. In February 2017 Mailgun spun back out of Rackspace as an independent company alongside a $50M investment led by Turn/River Capital with Scaleworks and Rackspace participating, relocating its center of gravity to San Antonio. Thoma Bravo began diligence in early 2018 and acquired the company in 2019 through its Discover middle-market fund, with Will Conway as CEO and Josh Odom as CTO; both are described as former executives as of the May 2025 podcast. Product documentation is now published under the Sinch brand.
Risks & controversies
Sources conflict on basic profile facts, including headquarters (San Antonio versus San Francisco), founder roster, current operating status (one directory marks the company "Inactive" while another marks it "active" and Y Combinator marks it "Acquired"), total funding ($1.0M versus $51.1M) and reported annual email volume (250 billion versus 400 billion versus 600 billion). One source attributes Mailgun's creation to Rackspace, contradicting the Y Combinator founder records. The business is also exposed to inbox providers such as Google and Microsoft actively filtering mail, which a Thoma Bravo partner identified as the core difficulty of delivering email at scale, and to a concentrated competitive set including SendGrid/Twilio and SparkPost/MessageBird.
Compiled by commissioned research from 8 cited public sources — announcements, filings, and press listed under research sources below.
Key figures
latest reportedCompany-reported or press-reported figures, each dated to when it was claimed — not independently audited.
Founder mafia
2 people who came through Mailgun went on to found or lead other companies.
Competitors · 3
by search overlap
Companies competing with Mailgun for the same Google search keywords, organic and paid, via search-intersection analysis.
Timeline · 3
launches, deals, and filingsThoma Bravo partner Hudson Smith states the firm got to know the business in early 2018 and acquired Mailgun in 2019, after also evaluating competitors SendGrid and SparkPost.
Mailgun, then based in San Antonio, Texas, secured $50M in funding led by Turn/River Capital with participation from Scaleworks and Rackspace. The investment and related spin-out transaction established Mailgun as a company independent of Rackspace, with proceeds intended to accelerate the product roadmap and drive growth.
$50M source ↗
Co-founder biography on Y Combinator's company page states Mailgun was acquired by Rackspace in 2012, after which co-founder Taylor Wakefield served as a Director in product at Rackspace for three years.
Dated company events from announcements, filings, and press; legal rows summarize public dockets and regulator releases.
In the news
▸Research sources · 8
primary sources listed
- Transactional Email API Service For Developers - Transactional Email API Service For Developers | Mailgunmailgun.com · web
8 public sources were cited for this profile; the first-party ones are listed here.
Frequently asked questions
- What does Mailgun do?
- Developer-focused email API platform for sending, receiving, tracking and validating transactional and marketing email.
- Who founded Mailgun?
- Mailgun was founded by Ev Kontsevoy, Taylor Wakefield.
- Who are Mailgun's investors?
- Mailgun's investors include Scaleworks, Spider Capital, Y Combinator, Salesforce Ventures, SV Angel.
- Where is Mailgun headquartered?
- Mailgun is headquartered in San Francisco, US.