Postmark vs Sparkpost
Compare Postmark and Sparkpost 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 | 4th of 10 → | 1 | 11 |
| <1M | 10th of 10 ↓ | 4 | 13 |
From February 11th to May 12th, Knock routed 25M–100M messages through Postmark and <1M through Sparkpost. Postmark reported 11 status page updates over the last 90 days, while Sparkpost reported 13.
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 February 11th to May 12th. The top-line number is an average of these daily values: Postmark averaged 24ms compared to 282ms for Sparkpost. Postmark's highest daily p50 was 57ms; Sparkpost's was 336ms. Postmark is 258ms 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 87ms compared to 348ms for Sparkpost. The highest daily p90 was 143ms for Postmark and 537ms for Sparkpost. Postmark handles these slower requests 261ms 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 231ms at p99 while Sparkpost reached 566ms. The highest daily p99 was 38235ms for Postmark and 31566ms for Sparkpost, 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% |
|---|---|---|---|---|---|
| 0.03% | 2.37% | Mar 27 | 86 | 2 |
| 0.16% | 3.41% | Feb 24 | 89 | 2 |
Averaged across the date range, Postmark shows a 0.03% daily error rate compared to 0.16% for Sparkpost. The highest single-day error rate was 2.37% for Postmark and 3.41% for Sparkpost. Postmark demonstrates a lower error rate, indicating slightly more consistent availability during this period. 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
Started Apr 21, 2026 — Resolved Apr 21, 2026
Good news - this issue has been resolved and everything should be working normally now. We're continuing to monitor closely to make sure everything stays stable. Thank you so much for your patience while we worked through this.
Started Apr 8, 2026 — Resolved Apr 9, 2026
**[UPDATE]** We determined that yesterday's network instability was caused by a widespread Google (Gmail) outage. You can find more information on Google’s Status Dashboard here: https://www.google.com/appsstatus/dashboard/incidents/224ozRqzW4sFBDK8hLnT We will share an additional update regarding our internal action items later today.
Started Apr 2, 2026 — Resolved Apr 3, 2026
**[UPDATE]** On **April 2nd** starting at **~07:00pm UTC**, Postmark experienced an incident that resulted in delayed message delivery and webhook notifications for some customers. The issue was caused by an infrastructure configuration change that disrupted internal mail routing. While messages were safely queued in a "Processing" state, they were not delivered until the routing configuration was restored. Service was restored on **April 3rd at ~4:20am UTC** and the backlog of queued message
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.
Recent Sparkpost incidents
Recent status page incidents for Sparkpost
Started May 12, 2026 — Resolved May 12, 2026
May 12, 09:38 EDT Resolved - This incident has been resolved.May 12, 09:10 EDT Monitoring - A fix has been implemented and we are monitoring the results.May 12, 08:48 EDT Identified - We’re currently investigating an issue that prevented some customers from updating their payment details. The root cause has been identified, and a fix is being implemented.
Started May 11, 2026 — Resolved May 11, 2026
May 11, 16:02 EDT Resolved - This incident has been resolved.May 11, 15:46 EDT Monitoring - A fix has been implemented and we are monitoring the results.May 11, 14:55 EDT Identified - We are experiencing an elevated level of errors and latency on the Suppression List API for some SparkPost customers. Please retry any 5xx error. Note: This issue does not impact SparkPost customers hosted in the EU.
Started May 9, 2026 — Resolved May 9, 2026
May 9, 18:17 EDT Resolved - This incident has been resolved.May 9, 18:05 EDT Monitoring - A fix has been implemented and we are monitoring the results.May 9, 17:50 EDT Identified - The issue has been identified and a fix is being implemented.May 9, 17:39 EDT Investigating - We are looking into why some messages are seeing delayed delivery.
Started May 8, 2026 — Resolved May 8, 2026
May 8, 07:31 EDT Resolved - This incident has been resolved.May 7, 06:49 EDT Monitoring - A fix has been implemented and we are monitoring the results.May 7, 05:31 EDT Investigating - We are currently investigating this issue.
Started Apr 5, 2026 — Resolved Apr 5, 2026
Apr 5, 15:01 EDT Resolved - Delivery rates to Apple domains have returned to normal with no further elevated delays or bounces. We will perform any necessary post-incident cleanup of suppression lists to ensure no recipients were incorrectly suppressed during the outage. NOTE: As of Monday April 5th at 9PM EDT the cleanup has been completed. All recipient addresses to Apple or Apple Private Relay domains that were suppressed during Apple's incident window were removed.Apr 5, 14:27 EDT Monito
Pros and cons
Postmark
Sparkpost
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
Pros
- Delivers nearly 40% of all commercial email worldwide
- Subaccount support for isolated sending streams under one billing account
- On-premise mail sending solution available for very high volume workloads
- Great analytics tools with predictive health scores for email deliverability
Cons
- No visual drag-and-drop email editor
- Less suited for high-volume marketing email
- Smaller feature set compared to all-in-one platforms
Cons
- Documentation can be hard to navigate with less beginner-friendly getting started content
- Higher price point than basic providers
- Now part of Bird (formerly MessageBird), which may affect product direction
Frequently asked questions
What is the difference between Postmark and Sparkpost?
Postmark is a transactional email service focused on fast, reliable delivery with transparent pricing. SparkPost is a data-driven email delivery platform with advanced analytics and predictive tools for high-volume senders. Postmark is best suited for transactional email, while Sparkpost is geared toward data-driven, high-volume.
Which is cheaper, Postmark or Sparkpost?
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+. Free tier includes 500 emails per month with community support. Paid plans start at $20/month for 50,000 emails with premium deliverability features. The best value depends on your sending volume. Use the pricing calculator above to compare costs at your expected volume.
Which is faster, Postmark or Sparkpost?
Based on real-world data from Knock, Postmark has a median API response time (p50) of 24ms compared to 282ms for Sparkpost.
Which is more reliable, Postmark or Sparkpost?
From February 11th to May 12th, Postmark showed an error rate of 0.03% while Sparkpost showed 0.16%. 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, Postmark or Sparkpost?
On the Knock platform, Postmark handled 25M–100M messages from February 11th to May 12th compared to <1M for Sparkpost. Postmark volume has remained stable, while Sparkpost is seeing declining volume.
Can I use both Postmark and Sparkpost together?
Yes. Knock enables you to integrate multiple email providers into a single notification workflow. You can use Postmark and Sparkpost 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 Postmark vs Sparkpost?
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. Sparkpost strengths include delivers nearly 40% of all commercial email worldwide and subaccount support for isolated sending streams under one billing account. On the other hand, Postmark drawbacks include no visual drag-and-drop email editor, while Sparkpost drawbacks include documentation can be hard to navigate with less beginner-friendly getting started content.
Use either provider with Knock
Knock enables you to integrate Postmark, Sparkpost, or any combination of email providers into a single notification workflow. Manage templates, orchestrate cross-channel delivery, and switch providers without changing your code.