Postmark, founded in 2010 and now owned by ActiveCampaign, is a transactional-only email service with message streams that separate transactional from…
Best for Postmark: Teams that want a service dedicated specifically to transactional email deliverability, with message streams keeping transactional and broadcast traffic separated, and that need up to 365-day data retention on a paid tier.
Best for Resend: Developer teams that want broad SDK language coverage (9 languages including Go, Rust, .NET, Laravel), React Email component-based templates, an MCP server for AI client integration, and SOC 2 Type II/GDPR compliance included on every plan.
At a Glance
Postmark
Resend
Primary category
Email Marketing
Email Marketing
Rating
Not documented
Not documented
Pricing model
Freemium
Freemium subscription with usage-based tiers
Starting price
Free (100 emails/month); paid plans start at $15/month
Free (3,000 emails/month); paid plans start at $20/month
Free plan
Yes
Yes
Free trial
Not documented
Not documented
Platforms
Web
Web
Team collaboration
Not documented
Not documented
AI features
Not documented
Yes
Public API
Yes
Yes
Key Differences
Company history and ownership
Postmark: Founded in 2010, now owned by ActiveCampaign.
Resend: No founding year or parent company is documented in the facts reviewed.
A longer, documented operating history and an established parent company can signal stability for teams prioritizing vendor longevity.
Transactional vs. marketing email
Postmark: Cons note it is primarily transactional-only, not a marketing campaign builder.
Resend: Offers separate Marketing (contact-based) pricing tracks — Free (1,000 contacts/month) and Pro ($40/month for 5,000 contacts) — alongside its Transactional tiers.
Teams needing both transactional and marketing/broadcast sending from one vendor avoid managing two separate providers.
AI client / MCP integration
Postmark: Not documented in the facts reviewed.
Resend: Provides an MCP server for integrating email sending into AI clients like Cursor and Claude, plus a monthly AI credit allotment on every plan.
Native MCP support lets AI coding assistants send email directly as part of an agentic workflow without custom integration work.
Free tier shape
Postmark: Free plan never expires, but is limited to 100 emails/month.
Resend: Free plan offers 3,000 emails/month but is capped at 100 emails/day and 1 domain.
A higher monthly cap with a daily limit suits bursty sending patterns differently than a lower flat monthly cap.
Data retention and compliance
Postmark: Retention can extend up to 365 days on the Pro tier.
Resend: Documents 30-day retention on its free tier and SOC 2 Type II plus GDPR compliance across all plans; longer retention tiers are not itemized in the facts reviewed.
Longer retention supports deeper historical analytics, while documented compliance certifications matter for procurement and security review.
Feature-by-Feature
Core Sending
Feature
Postmark
Resend
Email API
Available
Available
SMTP relay
Available
Available
Inbound email processing
Available
Available
Reusable email templates
Available
Not documented
React Email / component-based templates
Not documented
Available
Batch sending with open/link tracking
Not documented
Available
Developer Tools & AI
Feature
Postmark
Resend
CLI tool
Not documented
Available
MCP server for AI client integration
Not documented
Available
Official SDK language count
Available
Available
Pricing & Plans
Feature
Postmark
Resend
Free plan
Available
Available
Separate marketing-email pricing track
Unavailable
Available
Retention up to 365 days
Available
Not documented
SOC 2 Type II / GDPR compliance documented
Not documented
Available
Pricing Compared
Starting price reflects the lowest paid tier, not the full cost for every team size or usage level.
Postmark
Free — $0/month monthly
Basic — $15/month monthly
Pro — $16.50/month monthly
Platform — $18/month monthly
Enterprise — Custom (contact sales) custom
Resend
Free — $0 monthly
Pro — $20-$35/month monthly
Scale — $90-$1,150/month monthly
Enterprise — Custom custom
Pros & Cons
Postmark
Pros
Strong, long-standing reputation for transactional email deliverability
Clear, transparent usage-based pricing that scales with email volume
Developer-friendly API, SMTP support, and official libraries for major languages
Detailed per-message activity log and analytics
Now backed by ActiveCampaign's resources while still operating as a focused, standalone product
Cons
Free plan is limited to 100 emails per month, quite small for active testing
Strictly transactional focus means it's not a fit for teams wanting marketing email in the same tool
Per-email costs can add up for very high-volume senders compared to some bulk-oriented providers
Fewer built-in marketing-automation features than all-in-one platforms
Some users report a learning curve configuring custom domain authentication for optimal deliverability
Resend
Pros
Clean, modern developer experience with well-documented API and SDKs
Deep React Email integration for building emails in JSX
Generous free tier for small projects (3,000 emails/month)
Fast setup for transactional email in Node.js/TypeScript stacks
Strong deliverability tooling included out of the box
2024 price increases on higher Scale tiers upset some long-time customers
Marketing/broadcast features are billed separately from transactional email
Newer platform than incumbents like SendGrid or Mailgun, so track record is shorter
Daily send cap on the free plan (100 emails/day) limits testing at scale
Use Cases
Choose Postmark: Teams that want a service dedicated specifically to transactional email deliverability, with message streams keeping transactional and broadcast traffic separated, and that need up to 365-day data retention on a paid tier.
Choose Resend: Developer teams that want broad SDK language coverage (9 languages including Go, Rust, .NET, Laravel), React Email component-based templates, an MCP server for AI client integration, and SOC 2 Type II/GDPR compliance included on every plan.
Need both: Teams sending both transactional emails and separate marketing campaigns from contact lists may use Resend's marketing track for campaigns while keeping Postmark's stream-separated transactional service for reliable order/receipt/notification email.
Postmark
Transactional app emails — SaaS applications send password resets, welcome emails, and receipts reliably through Postmark's API.
E-commerce order notifications — Online stores send order confirmations, shipping updates, and account alerts with high deliverability.
Inbound reply handling — Support and helpdesk tools parse customer email replies into structured data using Postmark's inbound processing.
Resend
Transactional email for SaaS products — Send order confirmations, password resets, and one-time codes reliably via API or SMTP.
Marketing newsletters and broadcasts — Send contact-based newsletters and campaigns using Resend's separate marketing pricing track.
Product notification systems — Build automated, high-deliverability notification flows integrated directly into application code.
Frequently Asked Questions
Is there a free Postmark plan?
Yes, Postmark's free plan never expires and includes 100 emails/month.
Is there a free Resend plan?
Yes, Resend's free plan includes 3,000 emails/month (up to 100/day), 1 domain, and 5 AI credits/month.
Who owns Postmark?
Postmark is owned by ActiveCampaign; it was founded in 2010.
Can AI agents use Resend to send email?
Yes, Resend provides an MCP server for integration with AI clients such as Cursor and Claude, and plans include a monthly allotment of AI credits.
Does either support building emails as React components?
Resend supports React Email for building emails as components; this is not documented for Postmark.
How long can delivery data be retained?
Postmark's Pro tier allows retention up to 365 days. Resend documents 30-day retention on its free tier, with longer retention not itemized in the facts reviewed.