Compare Mandrill against Postmark API performance
Compare real-time performance, reliability, and uptime benchmarks for Mandrill and Postmark, 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) |
|---|---|---|---|---|
 | <1M | 7th of 10 → | 0 | 0 |
 | 10M–25M | 4th of 10 ↓ | 5 | 14 |
From August 13th to November 11th, Knock routed <1M messages through Mandrill and 10M–25M through Postmark. Mandrill reported 0 status page updates over the last 90 days, while Postmark reported 14.
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: Mandrill averaged 299ms compared to 59ms for Postmark. Mandrill's highest daily p50 was 378ms; Postmark's was 67ms. Postmark is 240ms 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, Mandrill has a p90 of 605ms compared to 83ms for Postmark. The highest daily p90 was 827ms for Mandrill and 107ms for Postmark. Postmark handles these slower requests 522ms 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, Mandrill reached 1466ms at p99 while Postmark reached 241ms. The highest daily p99 was 1980ms for Mandrill 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% | 0.08% | Sep 15 | 88 | 3 |
| 0.00% | 0.01% | Aug 30 | 89 | 0 |
Averaged across the date range, Mandrill shows a 0.00% daily error rate compared to 0.00% for Postmark. The highest single-day error rate was 0.08% for Mandrill 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 Mandrill incidents
Recent status page incidents for Mandrill
No incidents reported in the last 90 days
Recent Postmark incidents
Recent status page incidents for Postmark
Started Nov 5, 2026 — Resolved Nov 5, 2026
Latency around activity data looks to be back to normal. We will continue to monitor. Thanks for your patience.
Started Nov 4, 2026 — Resolved Nov 5, 2026
The maintenance is now complete. Thanks for your patience.
Started Nov 4, 2026 — Resolved Nov 4, 2026
Inbound processing is back to normal. The fix is holding, and all delayed messages have been delivered to your webhooks. We'll keep monitoring to make sure it stays that way.
Started Nov 3, 2026 — Resolved Nov 4, 2026
The maintenance is now complete. That took a lot longer than expected... we are going to schedule another maintenance window starting tomorrow, November 4th at 3PM Eastern.
Started Oct 27, 2026 — Resolved Oct 27, 2026
Resolved We've identified and resolved the issue affecting SMS two-factor authentication codes. Codes should now arrive as expected when you log in to your Postmark account. Sending email through Postmark wasn't affected. If you still don't receive a code, please contact support: https://postmarkapp.com/support Resolved at 14:50 EDT (18:50 UTC) - 27 October 2026.
Pros and cons
Compare the strengths and tradeoffs between Mandrill and Postmark.
Mandrill
Pros
- Friendly, well-laid-out developer documentation that makes integration straightforward
- Global infrastructure for fast delivery with dedicated IPs and IP address pools
- Solid analytics with reports on deliverability, opens, clicks, bounces, and rejections
- Reuse Mailchimp templates for transactional email with deep ecosystem integration
Cons
- Requires an existing Mailchimp Standard or Premium subscription
- Not available as a standalone service
- Higher cost than some dedicated transactional services
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
Pricing comparison
Compare Mandrill and Postmark as your email volume grows.
Frequently asked questions
Mandrill is a transactional email add-on for Mailchimp, suited for teams already using the Mailchimp platform. Postmark is a transactional email service focused on fast, reliable delivery with transparent pricing. Mandrill is best suited for mailchimp users needing transactional, while Postmark is geared toward transactional email.
Included as an add-on to Mailchimp Standard or Premium plans. Pricing is based on email blocks of 25,000 emails, starting at $20/block. Volume discounts apply: $18/block above 500K, scaling down to $10/block above 4M. 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. 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, Mandrill has a median API response time (p50) of 299ms compared to 59ms for Postmark.
From August 13th to November 11th, Mandrill 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.
On the Knock platform, Mandrill handled <1M messages from August 13th to November 11th compared to 10M–25M for Postmark. Mandrill volume has remained stable, while Postmark is seeing declining volume.
Yes. Knock enables you to integrate multiple email providers into a single notification workflow. You can use Mandrill and Postmark side by side, route traffic between them, or migrate from one to the other without changing your application code.
Mandrill strengths include friendly, well-laid-out developer documentation that makes integration straightforward and global infrastructure for fast delivery with dedicated ips and ip address pools. 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, Mandrill drawbacks include requires an existing mailchimp standard or premium subscription, while Postmark drawbacks include no visual drag-and-drop email editor.