Overview

Postmark is application email infrastructure for teams that need to send from their own products rather than manage a mailbox. It suits developers who want API or SMTP delivery and control over both transactional and promotional traffic. Its strongest case is the separation of those email types, though the free allowance is too small for more than light evaluation.

Key features

Teams can send through a REST API, SMTP, or multi-region SMTP routing. Official libraries cover Node.js, Python, Rails, Ruby, PHP, and .NET; broader integrations include Slack, Zapier, Stripe, WordPress, Supabase, Bubble, Craft CMS, Netlify, and Gravity Forms. SDKs, migration guides, dynamic API documentation, and event webhooks give developers several ways to fit Postmark into an existing stack.

Transactional and broadcast messages run through separate Message Streams and IP infrastructure. That distinction helps keep critical receipts or password resets apart from promotional mail. Inbound processing converts incoming messages to JSON and posts them to a webhook URL, useful when an application needs to handle replies or other incoming mail programmatically.

Responsive templates cover common transactional messages, including welcomes, password resets, receipts, invoices, and invitations; an editor and import tool are also available. Tracking covers delivery, bounces, spam, opens, and links. Full message content is retained for 45 days by default, with customization available. The maximum message size is 10 MB including content, headers, and attachments, and each message can have up to 50 recipients across To, CC, and BCC.

Security controls 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. Customer success support comes without a separate premium-support fee, with email, live chat, and one-on-one calls offered.

Pricing

The free Developer plan costs $0.00 USD per free and never expires, but caps sending at 100 emails per month with no overages. It is useful for a small proof of concept, not a live application with meaningful sending volume. The free trial does not require a credit card.

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 emails cost $1.80 per 1,000. Its four-user limit makes it the leanest paid fit for a small team that needs standard delivery and tracking.

Pro starts at $16.50 USD per month, billed monthly, also for 10,000 emails per month. It raises the allowance to six users and includes ten custom sending domains, inbound processing, and retention up to 365 days; extras cost $1.30 per 1,000. The modest increase over Basic is worthwhile when inbound handling or longer retention matters.

Platform starts at $18.00 USD per month, billed monthly, for the same 10,000-email starting quota. It includes unlimited custom sending domains and users, inbound processing, retention up to 365 days, and the lowest included overage rate at $1.20 per 1,000. It fits larger teams or multi-domain operations; teams sending beyond the starting quota still pay for extras. Unused emails do not roll over, and extra paid-plan email charges are calculated at the end of the billing cycle. Annual plans are not currently offered.

Custom activity retention starts at $5.00 USD per month and is available on Pro plans or higher. DMARC monitoring starts at $14.00 USD per month per domain. A dedicated IP starts at $50.00 USD per month per IP, for customers sending at least 300,000 emails per month on Pro or higher. High-volume plans have custom pricing.

Platforms

Postmark is available via API and web. Its iOS app was sunset in June 2025 and is no longer supported, so it is not an option for teams seeking a current iOS client.

Who it's for

Postmark is a good fit for product teams that need application email, event visibility, and a distinct route for transactional and broadcast mail. The API, SMTP options, and integrations suit stacks that already rely on developer workflows; inbound JSON processing is a further advantage for applications that consume email. A team with only a few test messages can start free, while production use should budget for a paid plan and possible overages.

Pros and cons

Pros: Separate transactional and broadcast infrastructure gives teams a way to keep promotional traffic apart from operational messages.
Pros: Flexible integration paths include REST API, SMTP, multi-region SMTP routing, official SDKs, integrations, and event webhooks.
Pros: Inbound processing and extended retention on Pro and Platform add workflow and audit value beyond outbound delivery.
Cons: The free plan stops at 100 emails per month and disallows overages, limiting its usefulness beyond evaluation.
Cons: Paid quotas are not rollover balances; unused email volume expires at the billing boundary, and extra sends add charges.
Cons: Larger-volume and dedicated-IP use costs more; dedicated IPs require at least 300,000 monthly sends and Pro or higher.

Alternatives

For a broader comparison, browse Transactional Email Software or Email Deliverability Software. Choose EasyDMARC when DMARC monitoring is the main need; its free plan includes one domain, 1,000 emails per month, 14 days of data history, and one invited user. GlockApps is another option for teams prioritizing spam tests and DMARC monitoring, with a free plan that includes two spam test credits and up to 10,000 DMARC messages. Choose Mailreach when email warming and spam testing are the priority; its All-In-One plan is $19.50 USD per month and includes at least 20 spam test credits and up to 100 emails per day.

TrueSend offers a free plan with 6,000 emails per month, two sending domains, a drag-and-drop builder, and more than 50 templates. MailMonitor is a paid alternative whose Deliverability Foundation starts at $1,000.00 USD per year. SenderSignal is a freemium, web-based alternative. DMARC Report is a freemium, web-based alternative, as is Mail-Tester.

Verdict

Choose Postmark if your team needs developer-oriented application email with separated transactional and promotional sending, useful delivery events, and an inbound processing path. Its API and SMTP choices make it a practical fit for an established stack, and Pro adds inbound email and longer retention at a small step above Basic. Look elsewhere if a 100-email free cap is insufficient for evaluation, if you need annual billing, or if your primary task is specialized deliverability or DMARC monitoring rather than application email.

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

Amazon SES vs Postmark

Amazon SES

Postmark