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Most buyers should pick Postmark.
Choose Postmark for transactional email when separate sending streams, inbound processing and official libraries for Node.js, Python, Ruby, PHP or .NET fit your stack. Choose Mailgun if you need email validation, previews, CRM data connections or a larger free allowance. Both provide hosted API and SMTP services, and both start paid plans at $15 per month. Compare usage beyond the included volume, since overage rates and higher-volume plan structures differ.
01Side by side
| Postmark | Mailgun | |
|---|---|---|
| Pricing model | Monthly plans; overages $1.20–$1.80 per 1,000 | Monthly plans; overages from $1.10 per 1,000 |
| Free tier | 100 emails/month; no overages | 100 emails/day; one domain, two API keys |
| API and SDKs | API and SMTP; official libraries for five languages | Email API and SMTP; SDKs listed |
| Docs and tooling | Migration guides for several email providers | Documentation, SDKs and a Cursor plugin |
| Integrations | Libraries and migration guides for named providers | CRM data connections and Cursor plugin |
| Deployment model | Hosted email API and SMTP service | Hosted email API and SMTP service |
| Platforms | Web | Web |
| Limits and scaling | Custom options from 1.5 million emails/month | Plans through 100,000 emails/month; enterprise available |
Postmark Choose Postmark if
- Choose Postmark if separate transactional and promotional streams matter.
- Choose Postmark if you want official libraries in its five listed languages.
- Choose Postmark if inbound processing is needed on Pro or higher.
Mailgun Choose Mailgun if
- Choose Mailgun if 100 free emails per day fits your test workload.
- Choose Mailgun if you need email validation and previews.
- Choose Mailgun if CRM data connections or its Cursor plugin fit your workflow.
02Pricing at real usage
Postmark’s Free plan includes 100 emails per month, with no overages allowed. Its Basic plan is $15 per month for 10,000 emails; Pro is $16.50 and Platform is $18 for the same included volume. Extra emails cost $1.80, $1.30 or $1.20 per 1,000 on those plans, respectively. Mailgun’s Free plan allows 100 emails per day. Its Basic plan costs $15 per month for 10,000 emails, Foundation $35 for 50,000 and Scale $90 for 100,000. Extra emails start at $1.80, $1.30 and $1.10 per 1,000 on those paid plans. Both list monthly billing and no annual pricing. At the same 10,000-email entry price, costs diverge as volume rises: compare Mailgun’s larger included tiers with Postmark’s lower-priced overages. Mailgun also charges separately for extra validations.
03API, SDKs and integration
Both products are hosted email services with API and SMTP sending. Postmark also processes inbound email into JSON and sends it to a webhook URL. Its official libraries are listed for Node.js, Python, Ruby, PHP and .NET. The service provides templates, analytics, link tracking and delivery statistics, and its migration guides cover SendGrid, Mailgun, Amazon SES, SparkPost, Mailchimp Transactional and Resend.
Mailgun’s API and SMTP services send, receive and track email. Its feature set also includes real-time or bulk email validation, email previews, incoming-message parsing and CRM data connections. The Mailgun site lists documentation and SDKs, but doesn’t name SDK languages in the product details. It also advertises a Cursor plugin. Neither product’s listed integration options specify a CLI, so check with the vendor if a command-line workflow is a requirement. Postmark’s named libraries make language fit easier to assess before implementation.
04Open source, self-hosting and lock-in
Neither vendor publishes open-source licensing, self-hosting options or a defined data-export path. Both are presented as hosted email services, so plan for vendor-managed delivery rather than deploying the sending system in your own environment. Postmark lists migration guides for several providers, including Mailgun; those guides can help scope a move, but they do not establish that templates, message history or other account data transfer automatically.
Before choosing either service, ask how to export message and event data, templates, suppression lists and configuration, and whether those exports remain available after cancellation. Also check how your application handles provider-specific message streams, inbound routes and webhooks. Keep email content and delivery logic behind an adapter if switching providers is a realistic future requirement; that reduces application changes, but does not remove the work of moving account data or validating deliverability.
Questions people ask
Is Postmark cheaper than Mailgun?
Both start at $15 per month for 10,000 emails. Postmark’s Pro and Platform plans cost $16.50 and $18 for that included volume; Mailgun’s next tiers are $35 for 50,000 and $90 for 100,000. Compare your likely volume and overage rates, not just the entry price.
Which service has the better free tier?
Mailgun lists 100 emails per day, one custom sending domain and two API keys on its Free plan. Postmark’s Free plan includes 100 emails per month and allows no overages. Mailgun offers the larger stated allowance; Postmark’s free plan does not expire.
Does Postmark support Mailgun migrations?
Postmark lists a Mailgun migration guide, alongside guides for several other email providers. Treat it as a starting point for planning the move, and confirm which account data and configuration you can transfer before scheduling a cutover.
Which is better for transactional email?
Both offer transactional email delivery through an API and SMTP. Postmark separates transactional and promotional messages into parallel sending infrastructure. Mailgun adds validation, previews and CRM data connections. Choose based on whether message-stream separation or those additional email tools better fit your system.