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) |
|---|---|---|---|---|
| 1M–10M | 4th of 10 ↓ | 4 | 12 |
| <1M | 10th of 10 ↓ | 3 | 6 |
From July 4th to October 2nd, Knock routed 1M–10M messages through Postmark and <1M through Sparkpost. Postmark reported 12 status page updates over the last 90 days, while Sparkpost reported 6.
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 July 4th to October 2nd. The top-line number is an average of these daily values: Postmark averaged 62ms compared to 335ms for Sparkpost. Postmark's highest daily p50 was 209ms; Sparkpost's was 554ms. Postmark is 273ms 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 209ms compared to 558ms for Sparkpost. The highest daily p90 was 250ms for Postmark and 648ms for Sparkpost. Postmark handles these slower requests 349ms 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 408ms at p99 while Sparkpost reached 727ms. The highest daily p99 was 1224ms for Postmark and 901ms 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% | Jul 4 | 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
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.
Recent Sparkpost incidents
Recent status page incidents for Sparkpost
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.)
Started Sep 14, 2026 — Resolved Sep 14, 2026
Sep 14, 12:46 EDT Resolved - The data has all been posted. We apologize for the delay. Sep 14, 12:31 EDT Monitoring - Data is reprocessed and loads are completing. Full data recovery expected in the next 30 minutes. Sep 14, 10:59 EDT Identified - We know what has caused the data delay and are working to get the data posted. Sep 14, 10:19 EDT Investigating - Health score and Cohort data is delayed.
Started Aug 27, 2026 — Resolved Aug 27, 2026
Aug 27, 18:56 EDT Resolved - The Apple bounce levels have maintained at pre incident levels during our monitoring phase. Our clean up of the bad suppressions has finished. This incident is resolved. Aug 27, 15:28 EDT Monitoring - We have seen recovery of the Apple private relay domain to pre-event bounce levels. Our team is actively working on automatically removing any suppressions that were created by this event. We anticipate the cleanup to be completed by 6PM EDT. Aug 27, 15:10 EDT
Started Aug 19, 2026 — Resolved Aug 19, 2026
Aug 19, 15:58 EDT Resolved - This incident has been resolved. Aug 19, 15:44 EDT Monitoring - A fix has been implemented and we are monitoring the results. Aug 19, 14:52 EDT Investigating - We are investigating an increase in delivery latency for some outbound messages. (NOTE: This does not impact our customers hosted in the US.)
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 62ms compared to 335ms for Sparkpost.
Which is more reliable, Postmark or Sparkpost?
From July 4th to October 2nd, 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.
Which is more popular, Postmark or Sparkpost?
On the Knock platform, Postmark handled 1M–10M messages from July 4th to October 2nd compared to <1M for Sparkpost. Postmark is currently seeing declining volume, 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.