At $0.10/1k emails, AWS SES is by far the cheapest transactional email API — 4× cheaper than the next option. Best for high-volume apps already on AWS.
⚡ Best for startups: Resend
$0.40/1k emails with a generous 3,000 free emails/month and excellent developer experience. React Email integration makes template building fast.
📬 Best deliverability: Postmark
Postmark charges a premium ($1.50/1k) but is optimized exclusively for transactional email — inbox rates are typically higher than bulk-sender APIs.
🔧 Best features: SendGrid
SendGrid offers the most mature ecosystem — A/B testing, click tracking, ISP feedback loops, and a massive sending infrastructure at $0.40/1k.