#postmark

The Best Email API for AI Agents in 2026: Who Actually Does Inbound and Outbound

Your AI agent needs to send and receive email through an API — and most providers only nail the sending half. A developer's deep-dive comparing Resend, Postmark, Mailgun, Amazon SES, SendGrid, MailerSend, Mailjet, and agent-native inboxes like AgentMail on the thing that actually matters: the inbound loop.