Pick a transactional email provider once and expect to live with it for years — migrating your sending domain’s reputation and every template to a new provider is real, annoying work. Here’s how the common options actually compare, not just on price.

The options

Amazon SES is the cheapest by a wide margin at volume, and it’s the obvious choice if you’re already on AWS and want one bill. The tradeoff is that you get almost no tooling — no template editor, minimal built-in analytics, bounce and complaint handling via SNS notifications you wire up yourself. You’re building the developer experience on top of a very cheap, very bare sending API.

Postmark is built specifically for transactional email (not marketing email) and it shows — fast delivery, strong deliverability out of the box, and a dashboard that actually shows you what happened to a specific email, down to the raw headers. It costs more per email than SES, and it enforces a strict split between transactional and marketing traffic (mixing them can get your account flagged), which is a feature if you only send transactional mail and friction if you don’t.

SendGrid covers both transactional and marketing email in one platform, with a bigger feature set — templates, A/B testing, marketing automation. That breadth is also the risk: SendGrid’s shared sending infrastructure has a spottier deliverability reputation than Postmark’s, because it’s easier for someone else’s marketing blast to affect the reputation pool you’re sending from, depending on your plan tier.

Resend is the newest of these, built by developers frustrated with the others’ APIs and dashboards. It’s a genuinely pleasant developer experience — clean API, React Email for templates — but it’s a younger company with less of a track record at scale than SES or Postmark, worth weighing if reliability history matters more than DX to you.

The comparison

	Best for	Deliverability reputation	Template tooling	Relative cost
SES	Cost at volume	Depends entirely on your setup	Minimal	Lowest
Postmark	Transactional-only apps	Strong, dedicated	Basic editor	Higher
SendGrid	Transactional + marketing in one tool	Good, shared-pool risk	Full-featured	Medium
Resend	Developer experience	Improving, less track record	React Email	Medium

What migration actually costs later

This is the part people underweight when picking a provider. Moving providers means:

• Re-verifying and re-pointing SPF/DKIM DNS records, which can cause a delivery gap if done wrong.
• Losing whatever sending reputation you built on the old provider’s shared IPs — a fresh warm-up period on the new one.
• Rewriting every template if you used the provider’s template syntax instead of rendering HTML yourself and just passing it through.

Minimize the second and third costs from day one: render your own HTML (with React Email, MJML, or plain templates) instead of building templates in a provider’s proprietary editor, and treat the provider as a dumb “send this HTML” API wherever you can. That keeps you free to switch providers without touching a single template later — the actual lock-in risk isn’t the provider, it’s the templates you built inside their tool.

The call

Under a few thousand emails a month and you’re not deep into AWS already, start with Postmark or Resend — the deliverability and debugging experience is worth the extra cost at low volume, where a few dollars a month barely registers. Move to SES once your volume makes the per-email cost difference real (tens of thousands of emails a month and up), and you’re comfortable building your own bounce/complaint handling around it. Use SendGrid only if you genuinely need transactional and marketing email in one platform — otherwise its broader feature set is paying for capability you won’t use.

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