Amazon SES vs Postmark
Compare Amazon SES and Postmark based on observed API performance, features, and pricing
Live performance comparison
Real-world performance data from messages sent through Knock
| Provider | Message volume | Growth | Status page updates (30d) | Status page updates (90d) |
|---|---|---|---|---|
 | 25M–100M | 3rd of 10 ↑ | 0 | 0 |
 | 25M–100M | 4th of 10 → | 5 | 11 |
From January 1st to March 31st, Knock routed 25M–100M messages through Amazon SES and 25M–100M through Postmark. Amazon SES reported 0 status page updates over the last 90 days, while Postmark reported 11.
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.
| Provider | Median (p50) | p90 | p95 | p99 |
|---|---|---|---|---|
| 144ms | 202ms | 231ms | 454ms |
| 31ms | 93ms | 120ms | 242ms |
The chart above shows each provider's daily median response time (p50) from January 1st to March 31st. The top-line number is an average of these daily values: Amazon SES averaged 144ms compared to 31ms for Postmark. Amazon SES's highest daily p50 was 165ms; Postmark's was 57ms. Postmark is 113ms 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, Amazon SES has a p90 of 202ms compared to 93ms for Postmark. The highest daily p90 was 244ms for Amazon SES and 143ms for Postmark. Postmark handles these slower requests 109ms 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, Amazon SES reached 454ms at p99 while Postmark reached 242ms. The highest daily p99 was 488ms for Amazon SES and 38235ms for Postmark, 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% | Feb 4 | 88 | 0 |
| 0.03% | 2.37% | Mar 27 | 83 | 4 |
Averaged across the date range, Amazon SES shows a 0.00% daily error rate compared to 0.03% for Postmark. The highest single-day error rate was 0.01% for Amazon SES and 2.37% for Postmark. 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 Amazon SES incidents
Recent status page incidents for Amazon SES
No incidents reported in the last 90 days
Recent Postmark incidents
Recent status page incidents for Postmark
Started Mar 27, 2026 — Resolved Mar 28, 2026
We've resolved the incident. Thanks for your patience.
Started Mar 26, 2026 — Resolved Mar 26, 2026
The issue has been resolved.
Started Mar 25, 2026 — Resolved Mar 25, 2026
The issue has been resolved! Thank you for patience.
Started Mar 8, 2026 — Resolved Mar 8, 2026
Resolved! Thank you for your patience.
Started Mar 4, 2026 — Resolved Mar 4, 2026
We've now resolved the incident. Thanks for your patience.
Pros and cons
Amazon SES
Postmark
Pros
- Delivers billions of emails per year for Netflix, Reddit, and Amazon
- Lowest cost per email among major providers with simple pay-as-you-go pricing
- Deep integration with the AWS ecosystem and SDKs in all major languages
- Highly scalable with no sending limits after warm-up
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
- Setup is complex with documentation that can be difficult to navigate
- New accounts are sandboxed to 200 messages per 24-hour period
- Accessing analytics requires additional AWS services like SNS and Lambda
Cons
- No visual drag-and-drop email editor
- Less suited for high-volume marketing email
- Smaller feature set compared to all-in-one platforms
Frequently asked questions
What is the difference between Amazon SES and Postmark?
Amazon SES is a cost-effective, cloud-scale email service built on AWS infrastructure. Postmark is a transactional email service focused on fast, reliable delivery with transparent pricing. Amazon SES is best suited for cost-sensitive, high-volume, while Postmark is geared toward transactional email.
Which is cheaper, Amazon SES or Postmark?
3,000 free emails per month for the first 12 months. After that, $0.10 per 1,000 emails with additional charges for attachments and dedicated IPs. Free tier includes 100 emails per month. Paid plans start at $15/month for 10,000 emails with overages at $1.80/1K up to 125K, and $1.70/1K at 300K+. The best value depends on your sending volume. Use the pricing calculator above to compare costs at your expected volume.
Which is faster, Amazon SES or Postmark?
Based on real-world data from Knock, Amazon SES has a median API response time (p50) of 144ms compared to 31ms for Postmark.
Which is more reliable, Amazon SES or Postmark?
From January 1st to March 31st, Amazon SES showed an error rate of 0.00% while Postmark showed 0.03%. Both rates are within acceptable thresholds for production email delivery, and Knock automatically retries failed requests to minimize the impact of transient errors.
Which is more popular, Amazon SES or Postmark?
On the Knock platform, Amazon SES handled 25M–100M messages from January 1st to March 31st compared to 25M–100M for Postmark. Amazon SES is currently trending upward in adoption, while Postmark volume has remained stable.
Can I use both Amazon SES and Postmark together?
Yes. Knock enables you to integrate multiple email providers into a single notification workflow. You can use Amazon SES and Postmark side by side, route traffic between them, or migrate from one to the other without changing your application code.
What are the main pros and cons of Amazon SES vs Postmark?
Amazon SES strengths include delivers billions of emails per year for netflix, reddit, and amazon and lowest cost per email among major providers with simple pay-as-you-go pricing. 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. On the other hand, Amazon SES drawbacks include setup is complex with documentation that can be difficult to navigate, while Postmark drawbacks include no visual drag-and-drop email editor.
Use either provider with Knock
Knock enables you to integrate Amazon SES, Postmark, or any combination of email providers into a single notification workflow. Manage templates, orchestrate cross-channel delivery, and switch providers without changing your code.