“What’s the cheapest transactional email API?” has two answers, because price flips with volume. This guide normalizes five major providers to a cost per 1,000 emails so you can compare directly. Figures are a June 2026 snapshot — always confirm on the vendor’s page.
Estimate — verify with each vendor. Email pricing changes and add-ons (dedicated IPs, validation, marketing streams) cost extra.
The answer first
| Provider | Headline price | Cost per 1,000 | Free tier |
|---|---|---|---|
| Amazon SES | $0.10 per 1,000 | $0.10 | 62k/mo only on EC2 |
| Resend | $20 / 50,000 | $0.40 | 3,000/month |
| SendGrid | $19.95 / 50,000 | $0.40 | 100/day forever |
| Mailgun | ~$35 / 50,000 | ~$0.70 | trial only |
| Postmark | $15 / 10,000 | $1.50 | trial only |
At scale, Amazon SES wins outright. See the full email API comparison for free tiers and pros/cons.
Why the cheapest provider changes with volume
The per-1,000 rate is only half the story. SendGrid, Resend, Mailgun and Postmark bundle a monthly base fee with an included allowance. So at very low volume, the forever-free tiers win:
- Under ~3,000/month: SendGrid (100/day) or Resend (3,000/month) are free.
- ~50,000/month: Resend and SendGrid Essentials (
$20) beat Postmark ($75) and Mailgun ($35). - Millions/month: Amazon SES at $0.10 per 1,000 is unbeatable — see the cheapest way to send 1 million emails.
Use the email cost calculator to find the winner at your volume.
Cheap isn’t always best
Amazon SES is the cheapest, but it is infrastructure, not a product — no UI templates, analytics or suppression out of the box, and deliverability is your job. Postmark is the most expensive per email yet is prized for fast transactional delivery. The right pick balances price against how much you want the provider to handle. Compare the close calls: SendGrid vs SES and Postmark vs Mailgun.
Sources and accuracy
Prices are snapshots of each vendor’s public pricing page captured in June 2026. They are estimates for general information; confirm current rates before relying on them. See our methodology.