Overview

Postmark is an application email service for delivering and tracking transactional and broadcast messages, with inbound email processing for applications that need it. It suits development teams that want API or SMTP delivery and a clear separation between operational and promotional mail. Its strongest case is that separation, supported by useful delivery tracking; its narrow free allowance and metered overages make volume planning important.

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, while integrations include Slack, Zapier, Stripe, WordPress, Supabase, Bubble, Craft CMS, Netlify, and Gravity Forms. Migration guides, dynamic API documentation, and event webhooks give developers practical ways to connect sending and delivery events to existing systems.

Transactional and broadcast mail run through separate Message Streams and IP infrastructure. That is a meaningful advantage when password resets and receipts should not share a sending path with promotional campaigns. Postmark also converts inbound messages into JSON and sends them to a webhook URL, useful for applications that need to process replies or other incoming mail.

Responsive templates cover common transactional messages such as welcome emails, password resets, receipts, invoices, and invitations; an editor and import tool are included. Tracking covers delivery, bounces, spam, opens, and links. 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 Deft data center is SOC 2 Type 2 accredited and that its infrastructure uses Deft and AWS with redundant servers. It offers support by email, live chat, and one-on-one calls, with customer success support included. Its iOS app was sunset in June 2025 and is no longer supported, so this is a web-and-API service rather than a supported iOS app.

Pricing

The free Developer plan costs 0.00 USD per free and provides 100 emails per month, with no overages and no expiration. It is a lasting way to evaluate a small integration, but the cap is too low for production sending beyond a very small workload.

Basic costs 15.00 USD per month, billed monthly, starting at 10,000 emails per month. It includes five custom sending domains, unlimited emails per day, 45-day data retention, and up to four users. Extra email costs $1.80 per 1,000 at the end of the billing cycle, and unused emails do not carry forward. This is the least expensive paid option, but its shorter retention and lack of inbound processing make it less suitable for teams that need those capabilities.

Pro costs 16.50 USD per month, billed monthly, starting at 10,000 emails per month. It raises the allowance to ten custom sending domains, permits up to six users, retains data for up to 365 days, and adds inbound email processing. Extra email costs $1.30 per 1,000. For a small step up from Basic, the longer retention and inbound processing are compelling; teams needing more than six seats should look higher.

Platform costs 18.00 USD per month, billed monthly, starting at 10,000 emails per month. It includes unlimited custom sending domains and users, unlimited emails per day, retention up to 365 days, and inbound processing. Extra email costs $1.20 per 1,000. Its modest price premium over Pro is most relevant to larger teams or those managing many domains.

Other charges include custom activity retention from $5 /month, available only on Pro plans or higher; DMARC monitoring from $14 /month per domain; and a dedicated IP from $50 /month per IP, available to Pro plans or higher sending at least 300,000 emails per month. High-volume plans have custom pricing. The free trial does not require a credit card, and annual plans are not offered.

Platforms

Postmark supports API and web access, with REST API, SMTP, and multi-region SMTP routing for delivery. Its iOS app is no longer supported.

Who it's for

Postmark is a strong fit for developers and product teams sending application email who value distinct infrastructure for transactional and broadcast traffic, event-level delivery visibility, and inbound webhook processing. Basic suits smaller workloads that can work within 45-day retention; Pro is a better fit when longer history or inbound mail matters; Platform is aimed at teams that need unlimited users or sending domains. It is less suitable for high-volume use without careful overage budgeting or for anyone looking for a supported iOS app.

Pros and cons

Pros: Separate infrastructure for transactional and broadcast mail helps keep operational messages distinct from campaigns.
Pros: API, SMTP, SDKs, templates, and event webhooks give development teams several integration paths and delivery signals.
Pros: Pro and Platform include inbound processing and up to 365 days of retention, while Platform removes user and custom-domain caps.
Cons: The free plan stops at 100 emails per month and does not permit overages, so it cannot absorb even modest growth.
Cons: Paid plans charge for extra email and do not roll unused volume forward, requiring teams with variable sending to watch their cycle totals.
Cons: Basic limits retention to 45 days and has no inbound processing, so the cheapest paid tier omits capabilities some application workflows need.

Alternatives

For email deliverability monitoring rather than application email delivery, consider EasyDMARC, which has a free plan with 1,000 emails per month, one domain, 14 days of history, and one invited user. GlockApps is another option for deliverability monitoring, with a free tier that includes two spam test credits and DMARC monitoring. For a sender focused on email warming and spam testing, Mailreach offers an All-In-One plan at 19.50 USD per month with at least 20 spam test credits and up to 100 emails per day. TrueSend is an alternative email sending service. SenderSignal, MailMonitor, Warmup Inbox, and DMARC Report are other options to compare. Browse Email Deliverability Software or Transactional Email Software for more choices.

Verdict

Choose Postmark if your application needs reliable separation of transactional and promotional mail, developer-friendly delivery methods, and detailed event tracking, with inbound processing available on Pro and above. The free tier is useful for a small trial, but its 100-email cap is restrictive; teams with larger or uneven volume should weigh paid overages against their sending needs. Look elsewhere if you need a supported iOS app or want a service centered on deliverability monitoring rather than sending.

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

Mailchimp vs Postmark

Mailchimp

Postmark