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 | 7th of 10 ↓ | 2 | 2 |
| 1M–10M | 4th of 10 ↓ | 4 | 12 |
From July 4th to October 2nd, Knock routed <1M messages through MailerSend and 1M–10M through Postmark. MailerSend reported 2 status page updates over the last 90 days, while Postmark reported 12.
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 |
|---|---|---|---|---|
| 162ms | 327ms | 393ms | 778ms |
| 62ms | 209ms | 227ms | 408ms |
The chart above shows each provider's daily median response time (p50) from July 4th to October 2nd. The top-line number is an average of these daily values: MailerSend averaged 162ms compared to 62ms for Postmark. MailerSend's highest daily p50 was 730ms; Postmark's was 209ms. Postmark is 100ms 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 327ms compared to 209ms for Postmark. The highest daily p90 was 3166ms for MailerSend and 250ms for Postmark. Postmark handles these slower requests 118ms 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 778ms at p99 while Postmark reached 408ms. 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% | 0.27% | Jul 21 | 90 | 1 |
| 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 0.27% 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
Ongoing since Sep 23, 2026
Status: Scheduled We will be carrying out scheduled maintenance. The work is expected to last no more than 30 minutes. During this period, the following services may be affected: • Application availability - application may be temporarily unavailable or load slowly. • API availability - our API may be temporarily unavailable. • Email sending - emails may experience delays. We recommend rescheduling any campaigns planned for this window to avoid issues. We apologize for any inconvenience Af
Started Sep 21, 2026 — Resolved Sep 21, 2026
Status: Complete 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 Sep 28, 2026 — Resolved Sep 28, 2026
This has been resolved. All inbound webhooks processing have been caught up. No messages have been lost.
Started Sep 28, 2026 — Resolved Sep 28, 2026
This incident has been resolved. The backlog of messages queued during the delay between 9:49 AM and 10:07 AM CT (10:49–11:07 AM ET) has been fully processed and delivered. New messages continue to be accepted and delivered normally. No messages were lost. If you have questions about a specific message, please reach out to us at [email protected].
Started Sep 22, 2026 — Resolved Sep 22, 2026
A subset of messages accepted between 2:15 pm and 2:35 pm EDT on September 22 (18:15 – 18:35 UTC) were held in queue due to a processing issue instead of being delivered immediately. Those messages were fully processed and delivered at 3:38 pm EDT on September 24 (19:38 UTC). No messages were lost. Messages accepted outside of this 20-minute window were not affected and were delivered normally. If you have questions about a specific message, please reach out to us at [email protected]
Started Sep 17, 2026 — Resolved Sep 17, 2026
Some users were experiencing problems with our service from 4:15 pm to 5:25 pm EDT, resulting in a page titled "Something went wrong". We have identified the root of the issue and have applied a remediating solution. If you are still encountering this page after clearing your site data, cache & cookies, please reach out to us at [email protected].
Started Aug 24, 2026 — Resolved Aug 24, 2026
We've now resolved the incident. Stats data has caught up and is now displaying in real time. This issue occurred from approximately 13:45 EDT to 16:25 EDT on August 24, 2026. Thank you 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 162ms compared to 62ms for Postmark.
Which is more reliable, MailerSend or Postmark?
From July 4th to October 2nd, 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.
Which is more popular, MailerSend or Postmark?
On the Knock platform, MailerSend handled <1M messages from July 4th to October 2nd compared to 1M–10M for Postmark. MailerSend is currently seeing declining volume, while Postmark is seeing declining volume.
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.