Postmark vs SendGrid
Compare Postmark and SendGrid 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 ↑ | 3 | 11 |
| 500M+ | 2nd of 10 → | 9 | 25 |
From March 3rd to June 1st, Knock routed 25M–100M messages through Postmark and 500M+ through SendGrid. Postmark reported 11 status page updates over the last 90 days, while SendGrid reported 25.
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 March 3rd to June 1st. The top-line number is an average of these daily values: Postmark averaged 16ms compared to 23ms for SendGrid. Postmark's highest daily p50 was 57ms; SendGrid's was 24ms. Both providers deliver comparable response times for the typical request.
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 81ms compared to 76ms for SendGrid. The highest daily p90 was 143ms for Postmark and 86ms for SendGrid. Both providers show similar performance at this percentile, indicating comparable consistency.
The 99th percentile (p99) represents the long tail — the slowest 1% of requests. Averaged across all days, Postmark reached 210ms at p99 while SendGrid reached 386ms. The highest daily p99 was 38235ms for Postmark and 4037ms for SendGrid, 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% |
|---|---|---|---|---|---|
| 0.02% | 2.37% | Mar 27 | 87 | 1 |
| 0.00% | 0.02% | Mar 24 | 87 | 2 |
Averaged across the date range, Postmark shows a 0.02% daily error rate compared to 0.00% for SendGrid. The highest single-day error rate was 2.37% for Postmark and 0.02% for SendGrid. 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 Jun 1, 2026 — Resolved Jun 2, 2026
The issue has been resolved as of approximately 6:50pm CT. Thank you for your patience.
Started May 28, 2026 — Resolved May 28, 2026
The issue has been resolved.
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.
Recent SendGrid incidents
Recent status page incidents for SendGrid
Started May 29, 2026 — Resolved May 29, 2026
May 29, 07:30 PDT Resolved - Customers have experienced elevated latency occurring in US East region from 6:30 AM to 8:58 AM Pacific time. Our engineers have investigated and resolved the issue. All impacted services are operating normally.
Started May 22, 2026 — Resolved May 22, 2026
May 22, 11:50 PDT Resolved - Our engineers have monitored the fix and confirmed the issue with SenderAuth and Whitelabel domains has been resolved. All services are now operating normally at this time. May 22, 10:51 PDT Monitoring - Our engineers have implemented a fix and are monitoring system performance. We will provide another update in an hour or as soon as more information becomes available. May 22, 10:30 PDT Investigating - Starting around 10:17AM on May 22 2026, our engineers bega
Started May 14, 2026 — Resolved May 14, 2026
May 14, 10:47 PDT Resolved - Our engineers have monitored the fix and confirmed the issue with Sender Engagement Quality (SEQ) API endpoint has been resolved. All services are now operating normally at this time. May 14, 10:12 PDT Monitoring - Our engineers have implemented a fix and are monitoring system performance. SendGrid Engagement Quality API endpoint is now working as expected with API keys. We will provide another update in 30 minutes or as soon as more information becomes available
Started May 13, 2026 — Resolved May 13, 2026
May 13, 08:30 PDT Resolved - Customers in US-East may have experienced intermittent high mail send latency from 5/13/2026 to 5/27/2026. Our engineers have investigated and resolved the issue. All impacted services are operating normally.
Started May 13, 2026 — Resolved May 13, 2026
May 12, 17:22 PDT Resolved - Our engineers have monitored the fix and confirmed all services are now operating normally. May 12, 16:48 PDT Monitoring - Between 16:10 PDT and 16:27 PDT on 05/12/2026, our engineers began investigating an issue with a subset of services experiencing 5xx errors. Users may have experienced issues when accessing subusers, authenticating domains and link branding records, accessing the account, and checking account stats. This does not impact mail send. Our eng
Pros and cons
Postmark
SendGrid
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
- Comprehensive documentation with SDKs for most major languages
- Rich analytics tools with programmatic API access to engagement data
- Strong focus on deliverability with AI-powered intelligent delivery
- Trusted by Uber, Booking.com, and Yelp for high-volume sending
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
- Extended email activity history requires a paid add-on
- Pricing can become complex at higher volumes
- Support response times vary by plan tier
Frequently asked questions
What is the difference between Postmark and SendGrid?
Postmark is a transactional email service focused on fast, reliable delivery with transparent pricing. SendGrid is a cloud-based email delivery platform owned by Twilio, known for high-volume transactional and marketing email. Postmark is best suited for transactional email, while SendGrid is geared toward high-volume transactional + marketing.
Which is cheaper, Postmark or SendGrid?
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 up to 100 emails per day for 60 days. Paid plans start at $19.95/month for 50,000 emails on the Essentials plan, with an Essentials 100K tier at $34.95/month. Pro plans with dedicated IPs start at $249/month for 300,000 emails. 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 SendGrid?
Based on real-world data from Knock, Postmark has a median API response time (p50) of 16ms compared to 23ms for SendGrid.
Which is more reliable, Postmark or SendGrid?
From March 3rd to June 1st, Postmark showed an error rate of 0.02% while SendGrid 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 SendGrid?
On the Knock platform, Postmark handled 25M–100M messages from March 3rd to June 1st compared to 500M+ for SendGrid. Postmark is currently trending upward in adoption, while SendGrid volume has remained stable.
Can I use both Postmark and SendGrid together?
Yes. Knock enables you to integrate multiple email providers into a single notification workflow. You can use Postmark and SendGrid 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 SendGrid?
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. SendGrid strengths include comprehensive documentation with sdks for most major languages and rich analytics tools with programmatic api access to engagement data. On the other hand, Postmark drawbacks include no visual drag-and-drop email editor, while SendGrid drawbacks include extended email activity history requires a paid add-on.
Use either provider with Knock
Knock enables you to integrate Postmark, SendGrid, or any combination of email providers into a single notification workflow. Manage templates, orchestrate cross-channel delivery, and switch providers without changing your code.