Mandrill vs Resend
Compare Mandrill and Resend 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 |
| 10M–25M | 1st of 10 → | 5 | 20 |
From March 3rd to June 1st, Knock routed 1M–10M messages through Mandrill and 10M–25M through Resend. Mandrill reported 0 status page updates over the last 90 days, while Resend reported 20.
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: Mandrill averaged 138ms compared to 88ms for Resend. Mandrill's highest daily p50 was 263ms; Resend's was 118ms. Resend is 50ms 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 362ms compared to 148ms for Resend. The highest daily p90 was 524ms for Mandrill and 192ms for Resend. Resend handles these slower requests 214ms 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 861ms at p99 while Resend reached 363ms. The highest daily p99 was 1341ms for Mandrill and 1410ms 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% |
|---|---|---|---|---|---|
| 0.01% | 0.43% | Apr 27 | 82 | 7 |
| 0.03% | 2.02% | Mar 20 | 84 | 4 |
Averaged across the date range, Mandrill shows a 0.01% daily error rate compared to 0.03% for Resend. The highest single-day error rate was 0.43% for Mandrill and 2.02% 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 May 26, 2026 — Resolved May 26, 2026
Status: Resolved We have resolved the underlying issue and service has been resumed. Affected components Broadcast Emails (Operational) Website (Operational) Single Email (Operational) Dashboard (Operational) Email Events (Operational) SMTP (Operational) Batch Emails (Operational) General API (Operational) Webhooks (Operational)
Started May 20, 2026 — Resolved May 20, 2026
Status: Complete We've completed our Email Events maintenance, and they are now showing the up-to-date status. Affected components Email Events (Operational)
Started May 8, 2026 — Resolved May 8, 2026
Status: Resolved We have resolved the underlying issue by reverting the unintended breaking change and service has been resumed. Affected components Dashboard (Operational) Batch Emails (Operational) General API (Operational) Single Email (Operational) Email Events (Operational) SMTP (Operational) Broadcast Emails (Operational) Webhooks (Operational) Website (Operational)
Started May 6, 2026 — Resolved May 6, 2026
Status: Resolved This incident is resolved. All failed provisioning requests have been reprocessed, and custom tracking domain creation is operating normally.
Started May 5, 2026 — Resolved May 5, 2026
Status: Complete We've successfully completed our maintenance, and the logs page is now behaving normally. Affected components Dashboard (Operational)
Pros and cons
Mandrill
Resend
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
- 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
- Requires an existing Mailchimp Standard or Premium subscription
- Not available as a standalone service
- Higher cost than some dedicated transactional services
Cons
- Newer and less battle-tested compared to incumbents like Mailgun or SendGrid
- Fewer enterprise features than established providers
- Limited marketing email capabilities
Frequently asked questions
What is the difference between Mandrill and Resend?
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.
Which is cheaper, Mandrill or Resend?
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.
Which is faster, Mandrill or Resend?
Based on real-world data from Knock, Mandrill has a median API response time (p50) of 138ms compared to 88ms for Resend.
Which is more reliable, Mandrill or Resend?
From March 3rd to June 1st, Mandrill showed an error rate of 0.01% while Resend showed 0.03%. 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 Resend?
On the Knock platform, Mandrill handled 1M–10M messages from March 3rd to June 1st compared to 10M–25M for Resend. Mandrill is currently seeing declining volume, while Resend volume has remained stable.
Can I use both Mandrill and Resend together?
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.
What are the main pros and cons of Mandrill vs Resend?
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.
Use either provider with Knock
Knock enables you to integrate Mandrill, Resend, or any combination of email providers into a single notification workflow. Manage templates, orchestrate cross-channel delivery, and switch providers without changing your code.