Compare Mandrill against Resend API performance
Compare real-time performance, reliability, and uptime benchmarks for Mandrill and Resend, 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 |
 | 1M–10M | 1st of 10 → | 4 | 4 |
From August 9th to November 7th, Knock routed <1M messages through Mandrill and 1M–10M through Resend. Mandrill reported 0 status page updates over the last 90 days, while Resend reported 4.
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 9th to November 7th. The top-line number is an average of these daily values: Mandrill averaged 305ms compared to 76ms for Resend. Mandrill's highest daily p50 was 382ms; Resend's was 96ms. Resend is 229ms 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 610ms compared to 109ms for Resend. The highest daily p90 was 827ms for Mandrill and 3499ms for Resend. Resend handles these slower requests 501ms 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 1487ms at p99 while Resend reached 412ms. The highest daily p99 was 1980ms for Mandrill and 10345ms for Resend, indicating the worst-case response time during spikes or provider-side congestion. Resend 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% | 0.09% | Oct 1 | 88 | 2 |
Averaged across the date range, Mandrill shows a 0.00% daily error rate compared to 0.00% for Resend. The highest single-day error rate was 0.08% for Mandrill and 0.09% for Resend. 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 Resend incidents
Recent status page incidents for Resend
Started Oct 26, 2026 — Resolved Oct 26, 2026
Status: Resolved Email status updates are processing normally again. All delayed updates have been delivered, and no data was lost. Affected components Email Events (Operational)
Started Oct 23, 2026 — Resolved Oct 23, 2026
Status: Resolved We have resolved the underlying issue and service has been resumed. Affected components Single Email (Operational) Broadcast Emails (Operational) Batch Emails (Operational) Scheduled Emails (Operational)
Started Oct 10, 2026 — Resolved Oct 10, 2026
Status: Resolved We have resolved the underlying issue and service has been resumed. Affected components Dashboard (Operational) General API (Operational) Webhooks (Operational)
Started Oct 9, 2026 — Resolved Oct 9, 2026
Status: Resolved We have resolved the underlying issue and service has been resumed. Affected components Dashboard (Operational) General API (Operational) Webhooks (Operational)
Pros and cons
Compare the strengths and tradeoffs between Mandrill and Resend.
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
Resend
Pros
- Beautiful documentation with attention to detail and great developer experience
- Created and maintain React Email, the go-to framework for building email templates in React
- Minimalist, developer-optimized platform that avoids bloat with a focused UI
- Transparent observability with real-time visibility into sends, failures, and engagement
Cons
- Newer and less battle-tested compared to incumbents like Mailgun or SendGrid
- Fewer enterprise features than established providers
- Limited marketing email capabilities
Pricing comparison
Compare Mandrill and Resend 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. Resend is a modern email API built for developers, with React Email support and a focus on simplicity. Mandrill is best suited for mailchimp users needing transactional, while Resend is geared toward developer-first, react teams.
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 3,000 emails per month and 100 emails per day. Paid plans start at $20/month for 50,000 emails with overages at $0.90/1K on Pro, scaling down to $0.46/1K on Scale 2.5M. 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 305ms compared to 76ms for Resend.
From August 9th to November 7th, Mandrill showed an error rate of 0.00% while Resend 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 9th to November 7th compared to 1M–10M for Resend. Mandrill volume has remained stable, while Resend volume has remained stable.
Yes. Knock enables you to integrate multiple email providers into a single notification workflow. You can use Mandrill and Resend 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. Resend strengths include beautiful documentation with attention to detail and great developer experience and created and maintain react email, the go-to framework for building email templates in react. On the other hand, Mandrill drawbacks include requires an existing mailchimp standard or premium subscription, while Resend drawbacks include newer and less battle-tested compared to incumbents like mailgun or sendgrid.