MailerSend vs Resend
Compare MailerSend 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 | 7th of 10 ↓ | 1 | 2 |
| 1M–10M | 1st of 10 → | 7 | 7 |
From July 24th to October 22nd, Knock routed <1M messages through MailerSend and 1M–10M through Resend. MailerSend reported 2 status page updates over the last 90 days, while Resend reported 7.
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.
| Provider | Median (p50) | p90 | p95 | p99 |
|---|---|---|---|---|
| 167ms | 349ms | 450ms | 1052ms |
| 83ms | 123ms | 167ms | 944ms |
The chart above shows each provider's daily median response time (p50) from July 24th to October 22nd. The top-line number is an average of these daily values: MailerSend averaged 167ms compared to 83ms for Resend. MailerSend's highest daily p50 was 730ms; Resend's was 96ms. Resend is 84ms 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, MailerSend has a p90 of 349ms compared to 123ms for Resend. The highest daily p90 was 3166ms for MailerSend and 3594ms for Resend. Resend handles these slower requests 226ms 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, MailerSend reached 1052ms at p99 while Resend reached 944ms. The highest daily p99 was 43537ms for MailerSend and 11263ms 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% | 0.00% | Jul 24 | 91 | 0 |
| 0.00% | 0.09% | Oct 1 | 82 | 6 |
Averaged across the date range, MailerSend shows a 0.00% daily error rate compared to 0.00% for Resend. The highest single-day error rate was 0.00% for MailerSend 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 MailerSend incidents
Recent status page incidents for MailerSend
Started Oct 11, 2026 — Resolved Oct 11, 2026
Status: Complete Maintenance has completed Affected components Delivery time (Operational) Email sending API (Operational) Email analytics (Operational) Deliverability rate (Operational) MailerSend APP (Operational) Bulk endpoint (Operational) SMTP (Operational) Email activity (Operational)
Started Sep 21, 2026 — Resolved Sep 21, 2026
Status: Complete Maintenance has completed Affected components Inbound routing (Operational) Bulk endpoint (Operational) SMTP (Operational) Delivery time (Operational) Email sending API (Operational)
Recent Resend incidents
Recent status page incidents for Resend
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 Webhooks (Operational) Dashboard (Operational) General API (Operational)
Started Oct 1, 2026 — Resolved Oct 1, 2026
Status: Resolved We have resolved the underlying issue and service has been resumed Affected components General API (Operational)
Ongoing since Oct 1, 2026
Status: Complete All systems are now fully operational Affected components Dashboard (Operational) Website (Operational)
Started Sep 26, 2026 — Resolved Sep 26, 2026
Status: Resolved We have resolved the underlying issue and service has been resumed. Affected components Webhooks (Operational)
Pros and cons
MailerSend
Resend
Pros
- Designed for both developers and business users with API and visual editor
- Modern, intuitive UI that is easier to navigate than older platforms
- Multi-channel support with native email and SMS transactional messaging
- Affordable Hobby plan at $7/month for 5,000 emails with low overage rates
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
- Available integrations with other tools are basic and limited
- Fewer advanced features than enterprise platforms
- Smaller ecosystem compared to established competitors
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
Mailersend is an intuitive transactional email and SMS service by Mailgun, designed for growing businesses. Resend is a modern email API built for developers, with React Email support and a focus on simplicity. MailerSend is best suited for growing saas + e-commerce, while Resend is geared toward developer-first, react teams.
Free tier includes 500 emails per month. Paid plans start at $7/month for 5,000 emails on the Hobby plan, with the Starter plan at $35/month for 50,000 emails. 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, MailerSend has a median API response time (p50) of 167ms compared to 83ms for Resend.
From July 24th to October 22nd, MailerSend 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, MailerSend handled <1M messages from July 24th to October 22nd compared to 1M–10M for Resend. MailerSend is currently seeing declining volume, while Resend volume has remained stable.
Yes. Knock enables you to integrate multiple email providers into a single notification workflow. You can use MailerSend and Resend side by side, route traffic between them, or migrate from one to the other without changing your application code.
MailerSend strengths include designed for both developers and business users with api and visual editor and modern, intuitive ui that is easier to navigate than older platforms. 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, MailerSend drawbacks include available integrations with other tools are basic and limited, 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 MailerSend, 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.