Compare Postmark against Sparkpost API performance
Compare real-time performance, reliability, and uptime benchmarks for Postmark and Sparkpost, 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) |
|---|---|---|---|---|
 | 10M–25M | 4th of 10 ↓ | 0 | 0 |
 | <1M | 10th of 10 ↓ | 2 | 8 |
From August 13th to November 11th, Knock routed 10M–25M messages through Postmark and <1M through Sparkpost. Postmark reported 0 status page updates over the last 90 days, while Sparkpost reported 8.
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 August 13th to November 11th. The top-line number is an average of these daily values: Postmark averaged 59ms compared to 317ms for Sparkpost. Postmark's highest daily p50 was 67ms; Sparkpost's was 525ms. 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 83ms compared to 540ms for Sparkpost. The highest daily p90 was 107ms for Postmark and 630ms for Sparkpost. Postmark handles these slower requests 457ms 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 241ms at p99 while Sparkpost reached 721ms. The highest daily p99 was 1224ms for Postmark and 931ms 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% |
|---|---|---|---|---|---|
| 0.00% | 0.01% | Aug 30 | 89 | 0 |
| 0.00% | 0.00% | Aug 13 | 91 | 0 |
Averaged across the date range, Postmark shows a 0.00% daily error rate compared to 0.00% for Sparkpost. The highest single-day error rate was 0.01% for Postmark and 0.00% for Sparkpost. 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 Postmark incidents
Recent status page incidents for Postmark
No incidents reported in the last 90 days
Recent Sparkpost incidents
Recent status page incidents for Sparkpost
Started Oct 31, 2026 — Resolved Oct 31, 2026
Oct 31, 13:23 EDT Resolved - This incident has been resolved. Oct 30, 16:02 EDT Identified - We have identified the issue and are working on a resolution; delivery latencies are recovering. Oct 30, 15:21 EDT Investigating - We are investigating a small increase in delivery latency for some outbound messages. (NOTE: This does not impact our customers hosted in the EU.)
Started Oct 28, 2026 — Resolved Oct 28, 2026
Oct 28, 16:37 EDT Resolved - This incident has been resolved. Oct 28, 16:37 EDT Monitoring - A fix was implemented and we are seeing sustained delivery recovery. Oct 28, 16:03 EDT Identified - We are continuing to work on a fix for this issue. Oct 28, 16:00 EDT Monitoring - A fix has been implemented and we are monitoring the results. Oct 28, 15:48 EDT Identified - The issue has been identified and a fix is being implemented. Oct 28, 15:37 EDT Investigating - We are investigating
Started Oct 11, 2026 — Resolved Oct 11, 2026
Oct 11, 16:57 EDT Resolved - This incident has been resolved. Oct 11, 14:17 EDT Monitoring - A fix has been implemented and we are monitoring the results. Oct 11, 14:17 EDT Update - We are continuing to work on a fix for this issue. Oct 11, 14:09 EDT Update - We are continuing to rollout the new root signing keys from ICANN. We continue to see recovery across our global clusters. Oct 11, 13:51 EDT Identified - We are investigating an increase in delayed (deferred) messages in both
Started Oct 1, 2026 — Resolved Oct 1, 2026
Oct 1, 13:36 EDT Resolved - This issue has been resolved. Since our changes went in, we've seen no further delivery delays, including through peak sending periods. Email is being delivered normally. We apologize for the disruption and thank you for your patience. Oct 1, 13:16 EDT Monitoring - We've made changes to address the intermittent delivery delays. Since then, email has been delivered without delay, including during peak sending periods that previously caused the slowdowns. We're wa
Started Sep 17, 2026 — Resolved Sep 17, 2026
Sep 17, 06:00 EDT Resolved - This incident has been resolved. Sep 17, 05:47 EDT Monitoring - A fix has been implemented and we are monitoring the results. Sep 17, 05:06 EDT Investigating - We are investigating an increase in delivery latency for some outbound messages. (NOTE: This does not impact our customers hosted in the EU.)
Pros and cons
Compare the strengths and tradeoffs between Postmark and Sparkpost.
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
Sparkpost
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
- 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
Pricing comparison
Compare Postmark and Sparkpost as your email volume grows.
Frequently asked questions
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.
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. 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.
Based on real-world data from Knock, Postmark has a median API response time (p50) of 59ms compared to 317ms for Sparkpost.
From August 13th to November 11th, Postmark showed an error rate of 0.00% while Sparkpost 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, Postmark handled 10M–25M messages from August 13th to November 11th compared to <1M for Sparkpost. Postmark is currently seeing declining volume, while Sparkpost is seeing declining volume.
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.
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.