MailerSend vs Mandrill
Compare MailerSend and Mandrill 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 | 9th of 10 → | 0 | 1 |
| 1M–10M | 8th of 10 ↓ | 0 | 0 |
From March 3rd to June 1st, Knock routed <1M messages through MailerSend and 1M–10M through Mandrill. MailerSend reported 1 status page update over the last 90 days, while Mandrill reported 0.
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 |
|---|---|---|---|---|
| 246ms | 513ms | 564ms | 851ms |
| 138ms | 362ms | 507ms | 861ms |
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: MailerSend averaged 246ms compared to 138ms for Mandrill. MailerSend's highest daily p50 was 586ms; Mandrill's was 263ms. Mandrill is 108ms 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 513ms compared to 362ms for Mandrill. The highest daily p90 was 1993ms for MailerSend and 524ms for Mandrill. Mandrill handles these slower requests 151ms 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 851ms at p99 while Mandrill reached 861ms. The highest daily p99 was 8277ms for MailerSend and 1341ms for Mandrill, indicating the worst-case response time during spikes or provider-side congestion. Both providers exhibit comparable tail response times, meaning neither is significantly more prone to outlier slowdowns.
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% | 0.07% | Apr 29 | 89 | 1 |
| 0.01% | 0.43% | Apr 27 | 82 | 7 |
Averaged across the date range, MailerSend shows a 0.00% daily error rate compared to 0.01% for Mandrill. The highest single-day error rate was 0.07% for MailerSend and 0.43% for Mandrill. 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 Apr 12, 2026 — Resolved Apr 12, 2026
Status: Complete Maintenance has completed Affected components MailerSend APP (Under maintenance)
Recent Mandrill incidents
Recent status page incidents for Mandrill
No incidents reported in the last 90 days
Pros and cons
MailerSend
Mandrill
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
- 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
- Available integrations with other tools are basic and limited
- Fewer advanced features than enterprise platforms
- Smaller ecosystem compared to established competitors
Cons
- Requires an existing Mailchimp Standard or Premium subscription
- Not available as a standalone service
- Higher cost than some dedicated transactional services
Frequently asked questions
What is the difference between MailerSend and Mandrill?
Mailersend is an intuitive transactional email and SMS service by Mailgun, designed for growing businesses. Mandrill is a transactional email add-on for Mailchimp, suited for teams already using the Mailchimp platform. MailerSend is best suited for growing saas + e-commerce, while Mandrill is geared toward mailchimp users needing transactional.
Which is cheaper, MailerSend or Mandrill?
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. 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. The best value depends on your sending volume. Use the pricing calculator above to compare costs at your expected volume.
Which is faster, MailerSend or Mandrill?
Based on real-world data from Knock, MailerSend has a median API response time (p50) of 246ms compared to 138ms for Mandrill.
Which is more reliable, MailerSend or Mandrill?
From March 3rd to June 1st, MailerSend showed an error rate of 0.00% while Mandrill showed 0.01%. 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, MailerSend or Mandrill?
On the Knock platform, MailerSend handled <1M messages from March 3rd to June 1st compared to 1M–10M for Mandrill. MailerSend volume has remained stable, while Mandrill is seeing declining volume.
Can I use both MailerSend and Mandrill together?
Yes. Knock enables you to integrate multiple email providers into a single notification workflow. You can use MailerSend and Mandrill 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 MailerSend vs Mandrill?
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. 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. On the other hand, MailerSend drawbacks include available integrations with other tools are basic and limited, while Mandrill drawbacks include requires an existing mailchimp standard or premium subscription.
Use either provider with Knock
Knock enables you to integrate MailerSend, Mandrill, or any combination of email providers into a single notification workflow. Manage templates, orchestrate cross-channel delivery, and switch providers without changing your code.