Mandrill vs Postmark
Compare Mandrill and Postmark 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 | 8th of 10 ↑ | 0 | 0 |
 | 25M–100M | 4th of 10 → | 5 | 10 |
From December 12th to March 12th, Knock routed 1M–10M messages through Mandrill and 25M–100M through Postmark. Mandrill reported 0 status page updates over the last 90 days, while Postmark reported 10.
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 December 12th to March 12th. The top-line number is an average of these daily values: Mandrill averaged 127ms compared to 33ms for Postmark. Mandrill's highest daily p50 was 238ms; Postmark's was 57ms. Postmark is 94ms 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 385ms compared to 91ms for Postmark. The highest daily p90 was 527ms for Mandrill and 112ms for Postmark. Postmark handles these slower requests 294ms 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 788ms at p99 while Postmark reached 208ms. The highest daily p99 was 4845ms for Mandrill and 648ms 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% | 0.22% | Feb 2 | 88 | 2 |
| 0.00% | 0.07% | Feb 4 | 85 | 4 |
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 0.22% for Mandrill and 0.07% 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
Status page incidents from the last 30 days for Mandrill
No incidents reported in the last 30 days
Recent Postmark incidents
Status page incidents from the last 30 days for Postmark
Started Mar 8, 2026 — Resolved Mar 8, 2026
Resolved! Thank you for your patience.
Started Mar 4, 2026 — Resolved Mar 4, 2026
We've now resolved the incident. Thanks for your patience.
Started Feb 26, 2026 — Resolved Feb 27, 2026
The incident has been resolved. Engineering will continue to monitor through the weekend. Long term system improvements and mitigation processes will continue to be a high priority effort. We appreciate and thank you for your patience.
Started Feb 23, 2026 — Resolved Feb 23, 2026
We've now resolved the incident. Thanks for your patience.
Started Feb 11, 2026 — Resolved Feb 12, 2026
We've resolved the issue. Thanks for your patience.
Pros and cons
Mandrill
Postmark
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
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
- Requires an existing Mailchimp Standard or Premium subscription
- Not available as a standalone service
- Higher cost than some dedicated transactional services
Cons
- No visual drag-and-drop email editor
- Less suited for high-volume marketing email
- Smaller feature set compared to all-in-one platforms
Frequently asked questions
What is the difference between Mandrill and Postmark?
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.
Which is cheaper, Mandrill or Postmark?
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 with overages at $1.80/1K up to 125K, and $1.70/1K at 300K+. The best value depends on your sending volume. Use the pricing calculator above to compare costs at your expected volume.
Which is faster, Mandrill or Postmark?
Based on real-world data from Knock, Mandrill has a median API response time (p50) of 127ms compared to 33ms for Postmark.
Which is more reliable, Mandrill or Postmark?
From December 12th to March 12th, 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.
Which is more popular, Mandrill or Postmark?
On the Knock platform, Mandrill handled 1M–10M messages from December 12th to March 12th compared to 25M–100M for Postmark. Mandrill is currently trending upward in adoption, while Postmark volume has remained stable.
Can I use both Mandrill and Postmark together?
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.
What are the main pros and cons of Mandrill vs Postmark?
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.
Use either provider with Knock
Knock enables you to integrate Mandrill, Postmark, or any combination of email providers into a single notification workflow. Manage templates, orchestrate cross-channel delivery, and switch providers without changing your code.