Mailgun is the granddaddy of email APIs. Launched in 2010, bought by Rackspace, then sold to Sinch. GitHub, Slack, Stripe, and Udemy send email through it. Nearly two decades on the market and billions of emails — they know everything there is to know about deliverability.
Website: mailgun.com
What It Can Do
The main thing — sending transactional emails: registration confirmations, password resets, payment notifications, alerts. Everything that must arrive instantly and reliably.
But that’s not the only use case. Mailgun supports bulk sending (newsletters, marketing), inbound email routing (receiving emails via API), attachment parsing, and an email validation API. The latter checks an address for validity before sending — saving your reputation.
SMTP and HTTP API are available simultaneously. You can start with SMTP (easier for legacy systems) and gradually move to the API (full control).
Integrations
SDKs for Python, Ruby, PHP, Node.js, Java, Go, C#. Official plugins for Laravel, Django, and Rails. If your framework isn’t on the list — curl always works.
Mailgun’s documentation is among the best in the market. Examples for every API method, a sandbox domain for testing, webhooks for tracking events (delivered, opened, clicked, complained).
Deliverability
Mailgun has its own IP pools and years of reputation management. SPF, DKIM, and DMARC are configured automatically when you add a domain. Dedicated IPs are available for high-volume senders (from $59/mo).
Built-in analytics show delivery rate, open rate, and complaint rate per domain. If metrics dip, the system highlights the issue before spam filters blacklist you.
Pricing
- Flex (pay-as-you-go): free for the first 100 emails/day, then $0.80 per 1,000 emails
- Foundation: $35/mo for 50,000 emails + custom domains
- Scale: $90/mo for 100,000 emails + dedicated IP
- Enterprise: custom
For startups, the Flex plan is sufficient: 3,000 free emails per month. You start paying when the project grows.
Weak Points
After the Sinch acquisition, the development pace slowed. Some users complain about support — responses take longer than before. The dashboard interface looks outdated compared to competitors.
SendGrid (Twilio) and Resend are breathing down their neck, offering more modern APIs and better DX. Mailgun wins on stability and expertise, but innovation has waned.
Verdict
Mailgun is a proven tool for sending email from code. Ideal for projects where deliverability and stability matter more than a trendy interface. The free tier is enough for testing, and the documentation covers every scenario. Recommended for transactional emails — Mailgun is still one of the best here.