Resend got the DX right
Resend built a genuinely good developer experience. The API is clean, the documentation is well-structured, the React Email integration is thoughtful, and the onboarding is fast. If you have used SendGrid or Mailchimp before, Resend feels like a significant step forward.
The free tier gives you 3,000 emails per month (capped at 100/day), one day of log retention, and a straightforward API key setup. For a side project or an early-stage product, it works well.
The gaps show up when you move to production scale or when something goes wrong.
What Resend does not ship
No warmup automation. If you are starting a new sending domain or migrating from another provider, you need to ramp volume gradually to build sender reputation. Resend does not do this automatically. You manage it yourself, which means daily limits, manual monitoring, and rollback plans when bounce rates spike. Most developers skip proper warmup and then spend weeks diagnosing deliverability problems that trace back to a cold domain.
No reputation isolation. Resend uses shared sending infrastructure. Your domain's reputation in their system is isolated at the DNS level (DKIM signing is per-domain), but the underlying sending infrastructure is pooled. If Resend's platform has a deliverability incident, it can affect your sending. You have no visibility into what is happening at the infrastructure level, and no way to move to isolated infrastructure without switching providers.
No BYOK option. If you have an AWS account and want to use your own SES infrastructure (for compliance, cost, or control reasons), Resend cannot accommodate that. You are on their infrastructure or you are not a customer.
One-day log retention on free tier. Debugging a failed email that went out 36 hours ago is not possible on the free plan. The paid Pro plan at $20/month extends this, but it is a limitation that matters when you are troubleshooting.
Transmit's approach
Transmit's DX is intentionally similar to Resend. The REST API structure is clean, the dashboard is fast, and sending your first email takes minutes. But the product is built on a different infrastructure model.
Managed mode provisions isolated sending infrastructure per organization. Your reputation is not shared with other customers on the platform, and warmup runs automatically.
BYOK mode connects to your own AWS SES account. If you already have SES set up, connecting via IAM role takes about 5 minutes. You pay AWS SES costs ($0.10/1k emails) plus a Transmit tier starting at $9/month.
Both modes include automated warmup, suppression management, sequences, and inbound routing.
Pricing comparison
| Transmit Managed | Transmit BYOK | Resend | |
|---|---|---|---|
| Free tier | No free managed tier | 1,000/mo (no CC) | 3,000/mo (100/day cap) |
| Starting price | $2/mo (3k emails) | $9/mo | $20/mo (Pro) |
| 50k emails/mo | ~$35/mo | ~$19/mo + AWS | $20/mo |
| 100k emails/mo | Custom | ~$49/mo + AWS | ~$65/mo |
| Log retention | 30 days | 30 days | 1 day (free), 30 days (Pro) |
| Reputation isolation | Per org | Your AWS account | Shared infrastructure |
| Automated warmup | Yes | Yes | No |
| BYOK (your own AWS) | No | Yes | No |
| Sequences (drip campaigns) | Yes | Yes | No |
| Inbound email routing | Yes | Yes | No |
| SMTP relay | Yes | Yes | Yes |
| MCP server for AI agents | Yes | Yes | No |
| React Email support | No (use React Email to generate HTML) | No (use React Email to generate HTML) | Yes |
The warmup gap in practice
Warmup is not optional. ISPs use sending history to calibrate inbox placement. A domain with no history that suddenly sends 10,000 emails on day one will see high spam folder placement regardless of content quality.
Resend's position is that you should handle warmup yourself or use a dedicated warmup service. That adds cost and complexity. More practically, most developers do not do it correctly because it requires discipline over weeks, not a one-time configuration.
Transmit's warmup scheduler monitors your domain's current sending reputation, ramps volume on a safe schedule, watches bounce and complaint rates in real time, and auto-pauses if thresholds are crossed. You configure your domain and let it run. Full details in the warmup documentation.
Sequences: automation Resend does not have
Resend is a sending API. It does not ship drip campaign automation or multi-step sequences. If you want to build an onboarding flow that sends a welcome email, a day-3 tips email, and a day-7 check-in email, you build that logic in your application.
Transmit's sequences handle this natively. You define steps with delays, a trigger (list enrollment or API), and per-contact state. The platform handles scheduling, sending, and tracking completion. This is meaningful for product teams building onboarding flows, re-engagement sequences, or post-purchase drips who do not want to maintain that scheduling infrastructure themselves.
Inbound email
Resend handles outbound only. Replies to your campaigns, support@ inboxes, and inbound routing flows are not in their product.
Transmit's inbound email routing lets you receive email at your verified domain, then route it: store in the dashboard, forward to an address, post to a webhook, or drop. This covers the common cases: reply tracking, support inbox automation, and email-based workflows.
BYOK: the path off shared infrastructure
If you are using Resend today and want to move to your own infrastructure without rebuilding your email stack, Transmit BYOK is the clearest path. You connect your AWS account, your existing domain DNS records carry over, and the same REST API format continues to work.
Transmit calls SES using your credentials. Email data is not routed through Transmit's infrastructure for sending. You keep the operational tooling (dashboards, warmup, sequences, suppression) while your traffic runs through your own AWS account.
More detail on the tradeoffs: Managed vs BYOK.
AI agent integration
Transmit ships an MCP server that exposes email sending, contact management, and list operations to AI agents and tools that support the Model Context Protocol. Resend has no equivalent. If you are building AI-powered workflows that need to send emails programmatically from an agent context, this is a practical difference.
The bottom line
Resend is a well-executed sending API that is genuinely pleasant to use. If you are building a side project or early-stage product, it works fine. The limitations (no warmup, shared infrastructure, no BYOK, limited log retention on free tier) become real issues once you are at production scale, trying to debug deliverability, or need infrastructure control for compliance reasons.
Transmit is built to cover the same DX ground while shipping the infrastructure layer that Resend deliberately skips.
Start for free with 1,000 emails per month on BYOK, no credit card required.