What is Mailgun?

What is Mailgun?

Mailgun came out of Y Combinator’s winter 2011 batch, founded in San Francisco by Ev Kontsevoy and Taylor Wakefield, and it has changed hands more often than anything else in this directory. Rackspace bought it in August 2012, then spun it back out as an independent company in February 2017 on a $50 million round led by Turn/River Capital. Thoma Bravo took a majority stake in 2019, combined it with Mailjet under the Pathwire brand, and sold the pair to Sweden’s Sinch in a deal valued at roughly $1.9 billion that closed in December 2021. It ships today as Sinch Mailgun.

It is sending infrastructure with two halves. Outbound goes through the HTTP API or the relay at smtp.mailgun.org, with a separate European stack at smtp.eu.mailgun.org where message data never leaves the region. Inbound is the half competitors rarely match: Mailgun publishes its own MX hosts and a Routes system of match and action expressions, so replies can be parsed and posted to your application instead of landing in a mailbox.

Two details that older write-ups get wrong. The pay-as-you-go Flex plan is retired and survives on legacy accounts only, and the free plan allows 100 emails a day rather than the thousands a month often quoted. Lyft, Microsoft, Wikipedia and DHL send through it.