Compare MailerSend against Postmark API performance
Compare real-time performance, reliability, and uptime benchmarks for MailerSend and Postmark, powered by proprietary data from billions of messages sent through Knock.
Live performance comparison
Real-world performance data from messages sent through Knock.
| Provider | Message volume | Growth | Status page updates (30d) | Status page updates (90d) |
|---|---|---|---|---|
 | <1M | 8th of 10 → | 0 | 2 |
 | 10M–25M | 4th of 10 ↓ | 5 | 14 |
From August 13th to November 11th, Knock routed <1M messages through MailerSend and 10M–25M through Postmark. MailerSend reported 2 status page updates over the last 90 days, while Postmark reported 14.
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 |
|---|---|---|---|---|
| 269ms | 467ms | 696ms | 1635ms |
| 59ms | 83ms | 106ms | 241ms |
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: MailerSend averaged 269ms compared to 59ms for Postmark. MailerSend's highest daily p50 was 730ms; Postmark's was 67ms. Postmark is 210ms 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, MailerSend has a p90 of 467ms compared to 83ms for Postmark. The highest daily p90 was 3166ms for MailerSend and 107ms for Postmark. Postmark handles these slower requests 384ms 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, MailerSend reached 1635ms at p99 while Postmark reached 241ms. The highest daily p99 was 43537ms for MailerSend and 1224ms 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% | 0.00% | Aug 13 | 91 | 0 |
| 0.00% | 0.01% | Aug 30 | 89 | 0 |
Averaged across the date range, MailerSend shows a 0.00% daily error rate compared to 0.00% for Postmark. The highest single-day error rate was 0.00% for MailerSend and 0.01% 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 MailerSend incidents
Recent status page incidents for MailerSend
Started Oct 11, 2026 — Resolved Oct 11, 2026
Status: Complete (Sun, 11 Oct 2026 07:10:00 GMT - Sun, 11 Oct 2026 07:40:00 GMT) Maintenance has completed Affected components Bulk endpoint (Operational) SMTP (Operational) Email activity (Operational) Delivery time (Operational) Email sending API (Operational) Email analytics (Operational) Deliverability rate (Operational) MailerSend APP (Operational)
Started Sep 21, 2026 — Resolved Sep 21, 2026
Status: Complete (Mon, 21 Sep 2026 07:00:00 GMT - Mon, 21 Sep 2026 07:05:00 GMT) Maintenance has completed Affected components Bulk endpoint (Operational) SMTP (Operational) Delivery time (Operational) Email sending API (Operational) Inbound routing (Operational)
Recent Postmark incidents
Recent status page incidents for Postmark
Started Nov 5, 2026 — Resolved Nov 5, 2026
Latency around activity data looks to be back to normal. We will continue to monitor. Thanks for your patience.
Started Nov 4, 2026 — Resolved Nov 5, 2026
The maintenance is now complete. Thanks for your patience.
Started Nov 4, 2026 — Resolved Nov 4, 2026
Inbound processing is back to normal. The fix is holding, and all delayed messages have been delivered to your webhooks. We'll keep monitoring to make sure it stays that way.
Started Nov 3, 2026 — Resolved Nov 4, 2026
The maintenance is now complete. That took a lot longer than expected... we are going to schedule another maintenance window starting tomorrow, November 4th at 3PM Eastern.
Started Oct 27, 2026 — Resolved Oct 27, 2026
Resolved We've identified and resolved the issue affecting SMS two-factor authentication codes. Codes should now arrive as expected when you log in to your Postmark account. Sending email through Postmark wasn't affected. If you still don't receive a code, please contact support: https://postmarkapp.com/support Resolved at 14:50 EDT (18:50 UTC) - 27 October 2026.
Pros and cons
Compare the strengths and tradeoffs between MailerSend and Postmark.
MailerSend
Pros
- Designed for both developers and business users with API and visual editor
- Modern, intuitive UI that is easier to navigate than older platforms
- Multi-channel support with native email and SMS transactional messaging
- Affordable Hobby plan at $7/month for 5,000 emails with low overage rates
Cons
- Available integrations with other tools are basic and limited
- Fewer advanced features than enterprise platforms
- Smaller ecosystem compared to established competitors
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
Pricing comparison
Compare MailerSend and Postmark as your email volume grows.
Frequently asked questions
Mailersend is an intuitive transactional email and SMS service by Mailgun, designed for growing businesses. Postmark is a transactional email service focused on fast, reliable delivery with transparent pricing. MailerSend is best suited for growing saas + e-commerce, while Postmark is geared toward transactional email.
Free tier includes 500 emails per month. Hobby is $7/month for 5,000 emails, with extra email at $1.50 per 1,000, and does not extend to 50,000 emails. Starter starts at $35/month for 50,000 emails and ends at 1 million. Professional starts at $110/month and published pricing ends at 2 million. 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. 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, MailerSend has a median API response time (p50) of 269ms compared to 59ms for Postmark.
From August 13th to November 11th, MailerSend showed an error rate of 0.00% while Postmark 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, MailerSend handled <1M messages from August 13th to November 11th compared to 10M–25M for Postmark. MailerSend volume has remained stable, while Postmark is seeing declining volume.
Yes. Knock enables you to integrate multiple email providers into a single notification workflow. You can use MailerSend and Postmark side by side, route traffic between them, or migrate from one to the other without changing your application code.
MailerSend strengths include designed for both developers and business users with api and visual editor and modern, intuitive ui that is easier to navigate than older platforms. 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, MailerSend drawbacks include available integrations with other tools are basic and limited, while Postmark drawbacks include no visual drag-and-drop email editor.