Overview

Postmark is application email infrastructure for teams that need dependable transactional messages alongside separate broadcast sending. It is best suited to developers who want API or SMTP delivery, inbound email handling, and visibility into delivery events.

Its strongest case is the separation of transactional and promotional traffic, backed by practical integration and tracking tools. The trade-off is a narrow free allowance and paid plans that charge for extra volume.

Key features

Postmark sends through REST API, SMTP, or multi-region SMTP routing. Official libraries cover Node.js, Python, Rails, Ruby, PHP, and .NET, while broader integrations include Slack, Zapier, Stripe, WordPress, Supabase, Bubble, Craft CMS, Netlify, and Gravity Forms. Migration guides, dynamic API documentation, and event webhooks should help teams connect it to existing workflows.

Transactional and broadcast messages use distinct Message Streams and IP infrastructure. That separation is useful when a product's password resets and receipts should not share a sending path with promotional campaigns. For inbound mail, Postmark converts messages into JSON and posts them to a webhook URL.

Responsive templates cover common transactional messages such as welcomes, password resets, receipts, invoices, and invitations, with an editor and import tool. Tracking covers delivery, bounces, spam, opens, and links. Full message content is retained for 45 days by default; longer retention is available on higher plans or as an add-on.

Operational safeguards include TLS and HTTPS, DKIM, SPF, DMARC, two-factor authentication, API permissions, penetration testing, and DDoS protection. Postmark says its primary data and servers use Deft and AWS, with redundant API, SMTP, inbound, and web servers; its Deft data center is SOC 2 Type 2 accredited. Each email is capped at 10 MB including headers and attachments, and each message can address at most 50 recipients across To, CC, and BCC. Customer success support is included, with email, live chat, and one-on-one calls.

Pricing

The free Developer plan costs 0.00 USD per free and never expires, but stops at 100 emails per month with no overages. It is useful for a small proof of concept, not an active application that sends regular customer mail. The no-credit-card free trial offers a way to evaluate the service without committing payment details.

Basic starts at 15.00 USD per month, billed monthly, for 10,000 emails per month. It includes five custom sending domains, unlimited emails per day, and 45-day retention; extra email costs $1.80 per 1,000. Its four-user limit and lack of inbound email processing make it the entry point for small teams with straightforward outbound needs.

Pro is 16.50 USD per month, billed monthly, starting at 10,000 emails per month. It raises the cap to six users, includes ten custom domains, inbound processing, and retention up to 365 days; additional volume is $1.30 per 1,000. For only $1.50 more than Basic, it is the more practical choice when inbound workflows or longer logs matter.

Platform costs 18.00 USD per month, billed monthly, and also starts at 10,000 emails. It adds unlimited custom sending domains and unlimited users, with inbound processing and retention up to 365 days; extra volume is $1.20 per 1,000. That makes it the clearest fit for larger teams or portfolios of sending domains, while the narrow price gap makes Basic harder to justify if its limits are restrictive.

Optional charges include custom activity retention from $5 /month on Pro or higher, DMARC monitoring from $14 /month per domain, and a dedicated IP from $50 /month per IP for customers sending at least 300,000 emails per month on Pro or higher. High-volume plans have custom pricing. Extra emails are calculated at the end of the billing cycle, unused emails do not roll over, and annual plans are not offered.

Platforms

Postmark is available through API and web. Its iOS app was sunset in June 2025 and is no longer supported, so it is not a choice for managing the service through a current iPhone app.

Who it's for

Postmark suits application teams that prioritize transactional delivery, need to keep it distinct from broadcast mail, or want inbound messages routed into a webhook-based workflow. Small teams can start on Basic, while Pro or Platform makes more sense when inbound processing, longer retention, more users, or additional domains justify the modest step up. It is less compelling for a project that needs more than 100 free monthly messages but cannot budget for a paid plan.

Pros and cons

Pros: Separate transactional and broadcast infrastructure helps keep distinct email jobs apart.
Pros: Inbound-to-JSON processing, event webhooks, and broad integration support fit application workflows.
Pros: Pro and Platform add longer retention and inbound processing for a small monthly increase over Basic.
Cons: The free plan's 100-email monthly ceiling and ban on overages make it unsuitable for ongoing production use.
Cons: Basic stops at four users and five custom domains, and lacks inbound processing.
Cons: Unused volume expires each billing period, and annual billing is unavailable.

Alternatives

For a broader shortlist, compare Email Deliverability Software and Transactional Email Software. Choose EasyDMARC if a free DMARC-focused option with 1,000 emails per month and 14 days of data history better fits the task. GlockApps is worth considering when the free tier's spam-test credits and DMARC monitoring are more relevant than application email delivery. Pick Mailreach when email warming and spam testing are the priority; its All-In-One plan is $19.50 USD per month and allows up to 100 emails per day.

SenderSignal, TrueSend, Mail-Tester, Palisade, and Suped are also alternatives to compare.

Verdict

Postmark is a strong fit for developers building applications that need tracked transactional email, separate broadcast streams, or inbound mail routed to webhooks. Its clear plan progression and integration options support growing use, but the 100-message free cap and paid overage model rule it out for teams seeking substantial free sending. Choose it for application email infrastructure; look elsewhere if deliverability testing or a lasting free sending allowance matters more.

	Mailgun	Postmark
Free plan	Yes	Yes
Free trial	No	Yes
Paid from	Free	$5/mo
Open source	No	No
Platforms	Web	api, Web
Free plan	Yes	Yes
Dedicated IP option	Yes	Yes
Monthly send limit	10,000 emails/mo	10,000 emails/mo
Paid from	—	15 /mo

Mailgun vs Postmark

Mailgun

Postmark