Mailersend vs Postmark
Compare Mailersend 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) |
|---|---|---|---|---|
 | <1M | 8th of 10 ↑ | 2 | 3 |
 | 25M–100M | 4th of 10 → | 5 | 11 |
From January 1st to March 31st, Knock routed <1M messages through Mailersend and 25M–100M through Postmark. Mailersend reported 3 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 |
|---|---|---|---|---|
| 264ms | 548ms | 589ms | 802ms |
| 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: Mailersend averaged 264ms compared to 31ms for Postmark. Mailersend's highest daily p50 was 469ms; Postmark's was 57ms. Postmark is 233ms 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 548ms compared to 93ms for Postmark. The highest daily p90 was 1048ms for Mailersend and 143ms for Postmark. Postmark handles these slower requests 455ms 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 802ms at p99 while Postmark reached 242ms. The highest daily p99 was 12094ms for Mailersend 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% |
|---|---|---|---|---|---|
| 0.01% | 0.06% | Feb 18 | 84 | 4 |
| 0.03% | 2.37% | Mar 27 | 83 | 4 |
Averaged across the date range, Mailersend shows a 0.01% daily error rate compared to 0.03% for Postmark. The highest single-day error rate was 0.06% for Mailersend 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 Mailersend incidents
Recent status page incidents for Mailersend
Ongoing since Mar 30, 2026
Status: Scheduled Our database service provider will be performing scheduled maintenance that should take no longer than 15 minutes. During this time, you may experience brief interruptions when signing up, logging in, or switching accounts on MailerSend. We appreciate your patience and thank you for your continued trust in our services. Affected components MailerSend APP (Under maintenance)
Started Mar 3, 2026 — Resolved Mar 3, 2026
Status: Complete Maintenance has completed Affected components Bulk endpoint (Under maintenance) SMTP (Under maintenance) Delivery time (Under maintenance) Email sending API (Under maintenance) Deliverability rate (Under maintenance)
Started Feb 19, 2026 — Resolved Feb 19, 2026
Status: Resolved The issue has been resolved and systems have returned to normal. We’ll continue monitoring to ensure ongoing stability. Thank you for your patience. Affected components MailerSend APP (Operational)
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
Mailersend
Postmark
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
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
- Available integrations with other tools are basic and limited
- Fewer advanced features than enterprise platforms
- Smaller ecosystem compared to established competitors
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 Mailersend and Postmark?
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.
Which is cheaper, Mailersend or Postmark?
Free tier includes 500 emails per month. Paid plans start at $7/month for 5,000 emails on the Hobby plan, with the Starter plan at $35/month for 50,000 emails. 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, Mailersend or Postmark?
Based on real-world data from Knock, Mailersend has a median API response time (p50) of 264ms compared to 31ms for Postmark.
Which is more reliable, Mailersend or Postmark?
From January 1st to March 31st, Mailersend showed an error rate of 0.01% 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, Mailersend or Postmark?
On the Knock platform, Mailersend handled <1M messages from January 1st to March 31st compared to 25M–100M for Postmark. Mailersend is currently trending upward in adoption, while Postmark volume has remained stable.
Can I use both Mailersend and Postmark together?
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.
What are the main pros and cons of Mailersend vs Postmark?
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.
Use either provider with Knock
Knock enables you to integrate Mailersend, 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.