Compare Postmark against Resend API performance
Compare real-time performance, reliability, and uptime benchmarks for Postmark and Resend, powered by proprietary data from billions of messages sent through Knock.
Best email messaging software for transactional notifications
Based on billions of messages sent through Knock from August 13th to November 11th (updated daily):
- Fastest email API: SendGrid (14ms median, 100M–500M messages)
- High volume at scale: SendGrid, Mailgun, Amazon SES (14ms median, 121ms median, 168ms median, 100M–500M messages)
- Fastest-growing adoption: Resend (Growth rank 1 of 10, 10M–25M messages)
See the full benchmarks for complete rankings and methodology.
Live performance comparison
Real-world performance data from messages sent through Knock.
| Provider | Message volume | Growth | Status page updates (30d) | Status page updates (90d) |
|---|---|---|---|---|
 | 10M–25M | 4th of 10 ↓ | 0 | 0 |
 | 10M–25M | 1st of 10 → | 2 | 2 |
From August 13th to November 11th, Knock routed 10M–25M messages through Postmark and 10M–25M through Resend. Postmark reported 0 status page updates over the last 90 days, while Resend reported 2.
Response time
Response time measures how long each provider takes to accept an API request from Knock, including connection overhead and any automatic retries. Lower values mean faster message hand-off.
The chart above shows each provider's daily median response time (p50) from August 13th to November 11th. The top-line number is an average of these daily values: Postmark averaged 59ms compared to 70ms for Resend. Postmark's highest daily p50 was 67ms; Resend's was 96ms. Postmark is 11ms faster at the median, which can add up at high volumes.
The 90th percentile (p90) captures the slowest 10% of requests, revealing how each provider handles moderate stress. Averaged across all days, Postmark has a p90 of 83ms compared to 102ms for Resend. The highest daily p90 was 107ms for Postmark and 146ms for Resend. Postmark handles these slower requests 19ms faster, suggesting more consistent performance across the board.
The 99th percentile (p99) represents the long tail — the slowest 1% of requests. Averaged across all days, Postmark reached 241ms at p99 while Resend reached 304ms. The highest daily p99 was 1224ms for Postmark and 1793ms for Resend, indicating the worst-case response time during spikes or provider-side congestion. Postmark shows a tighter tail, which may matter for time-sensitive notifications like one-time passwords or real-time alerts where even rare delays can impact user experience.
Error rate
Error rate tracks the ratio of 5xx responses and timeouts to total requests. Knock automatically retries failed requests, so transient provider errors rarely affect end-user delivery.
| Provider | Avg. daily error rate | Highest daily rate | Peak error date | Zero-error days | Days above 0.01% |
|---|---|---|---|---|---|
| 0.00% | 0.01% | Aug 30 | 89 | 0 |
| 0.00% | 0.09% | Oct 1 | 89 | 2 |
Averaged across the date range, Postmark shows a 0.00% daily error rate compared to 0.00% for Resend. The highest single-day error rate was 0.01% for Postmark and 0.09% for Resend. Both providers show similar reliability levels, with error rates well within acceptable thresholds. Knock automatically retries failed requests to both providers, minimizing the impact of transient errors on end-user delivery.
About these metrics: Data represents messages sent through Knock during the specified period. Response time measures time from Knock to provider acceptance. Error rate includes only provider 5xx responses and timeouts.
Recent Postmark incidents
Recent status page incidents for Postmark
No incidents reported in the last 90 days
Recent Resend incidents
Recent status page incidents for Resend
Started Oct 26, 2026 — Resolved Oct 26, 2026
Status: Resolved Email status updates are processing normally again. All delayed updates have been delivered, and no data was lost. Affected components Email Events (Operational)
Started Oct 23, 2026 — Resolved Oct 23, 2026
Status: Resolved We have resolved the underlying issue and service has been resumed. Affected components Single Email (Operational) Broadcast Emails (Operational) Batch Emails (Operational) Scheduled Emails (Operational)
Pros and cons
Compare the strengths and tradeoffs between Postmark and Resend.
Postmark
Pros
- Excellent deliverability with separate infrastructure for transactional and bulk messages
- Publishes time-to-inbox data across major email providers for transparency
- Great documentation with official and community-supported SDKs for all major languages
- 45-day message and log retention on all plans
Cons
- No visual drag-and-drop email editor
- Less suited for high-volume marketing email
- Smaller feature set compared to all-in-one platforms
Resend
Pros
- Beautiful documentation with attention to detail and great developer experience
- Created and maintain React Email, the go-to framework for building email templates in React
- Minimalist, developer-optimized platform that avoids bloat with a focused UI
- Transparent observability with real-time visibility into sends, failures, and engagement
Cons
- Newer and less battle-tested compared to incumbents like Mailgun or SendGrid
- Fewer enterprise features than established providers
- Limited marketing email capabilities
Pricing comparison
Compare Postmark and Resend as your email volume grows.
Frequently asked questions
Postmark is a transactional email service focused on fast, reliable delivery with transparent pricing. Resend is a modern email API built for developers, with React Email support and a focus on simplicity. Postmark is best suited for transactional email, while Resend is geared toward developer-first, react teams.
Free tier includes 100 emails per month. Paid plans start at $15/month for 10,000 emails on Basic, $16.50/month on Pro, and $18/month on Platform. Published pricing ends at 1.5 million emails per month. Free tier includes 3,000 emails per month and 100 emails per day. Paid plans start at $20/month for 50,000 emails with overages at $0.90/1K on Pro, scaling down to $0.46/1K on Scale 2.5M. The best value depends on your sending volume. Use the pricing calculator above to compare costs at your expected volume.
Based on real-world data from Knock, Postmark has a median API response time (p50) of 59ms compared to 70ms for Resend.
From August 13th to November 11th, Postmark showed an error rate of 0.00% while Resend showed 0.00%. Both rates are within acceptable thresholds for production email delivery, and Knock automatically retries failed requests to minimize the impact of transient errors.
On the Knock platform, Postmark handled 10M–25M messages from August 13th to November 11th compared to 10M–25M for Resend. Postmark is currently seeing declining volume, while Resend volume has remained stable.
Yes. Knock enables you to integrate multiple email providers into a single notification workflow. You can use Postmark and Resend side by side, route traffic between them, or migrate from one to the other without changing your application code.
Postmark strengths include excellent deliverability with separate infrastructure for transactional and bulk messages and publishes time-to-inbox data across major email providers for transparency. Resend strengths include beautiful documentation with attention to detail and great developer experience and created and maintain react email, the go-to framework for building email templates in react. On the other hand, Postmark drawbacks include no visual drag-and-drop email editor, while Resend drawbacks include newer and less battle-tested compared to incumbents like mailgun or sendgrid.