I don't want a huge email marketing platform. I just need an API. What should I use?

If you just want an API for sending emails—not a full marketing platform—you probably want a transactional email service.

Good options

1. Postmark

Best if you want:

• very reliable delivery
• simple API
• transactional emails only
• clean logs and templates

Great for: password resets, receipts, notifications, app emails.
Not ideal for: big bulk marketing campaigns.

2. SendGrid

Best if you want:

• a broad feature set
• easy API
• transactional + some marketing capability
• lots of integrations

Great for: apps that may grow into more email needs.
Tradeoff: can feel a bit heavier than necessary.

3. Mailgun

Best if you want:

• developer-friendly API
• good for programmatic sending
• flexible setup
• inbound routing/webhooks

Great for: apps, SaaS, and custom email workflows.
Tradeoff: UI and setup can be more technical.

4. Amazon SES

Best if you want:

• very low cost
• strong scalability
• raw sending infrastructure

Great for: high-volume sending and cost-sensitive projects.
Tradeoff: more setup and less convenience than others.

5. Resend

Best if you want:

• modern API
• simple developer experience
• easy integration with apps
• good for product emails

Great for: startups and modern web apps.
Tradeoff: newer than the long-established players.

My quick recommendation

• Best overall simple API: Postmark
• Best low cost: Amazon SES
• Best developer-friendly modern option: Resend
• Best all-around if you might need more later: SendGrid

What to avoid if you just need an API

Avoid full marketing suites like:

• Mailchimp
• HubSpot
• Klaviyo

They’re great for campaigns and automation, but usually too heavy if you only need to send emails programmatically.

If you tell me:

1. your volume,
2. whether emails are transactional or marketing,
3. your stack (Node, Python, etc.),

I can recommend the best one for your exact use case.