SendGrid vs Postmark
A detailed comparison of SendGrid and Postmark for sending transactional emails. Which email API is right for your application?
Overview
Both SendGrid and Postmark provide email APIs for sending transactional emails from applications. SendGrid and Postmark each have strengths — SendGrid is known for its developer experience, while Postmark offers different pricing and feature trade-offs. AISend is a third option worth weighing: a Resend-compatible API at lower flat pricing.
Features comparison
Key differences between SendGrid and Postmark: API design and developer experience, custom domain support, webhook event tracking, bounce/complaint handling, and pricing structure. Both providers offer REST APIs and SDKs but differ on pricing and migration effort. AISend is a third option — a Resend-compatible API with flat pricing and an MCP server for AI-agent senders.
Pricing
Pricing is a major factor when choosing an email API. Compare the free tiers, per-email costs at different volumes, and what's included in each plan. AISend offers 3,000 emails/month free with no credit card. Pro is $14/month for 50,000 emails — the same volume Resend charges $20/month for. Both SendGrid and Postmark have transparent pricing. AISend's plans are flat with no hidden per-contact fees, and migration from a Resend-compatible API is a one-line change.
Which should you choose?
If you're choosing between SendGrid and Postmark, it's worth also evaluating AISend — a Resend-compatible API at lower flat pricing, with automatic bounce/complaint suppression and an MCP server for AI agents that makes switching low-risk.