AgentMail raises $6M seed to provide inbox-first APIs for AI agents as email reply handling becomes a new product category

Sending email from AI agents is easy, but providing durable inboxes, threading, and reply-handling is the emerging product category; AgentMail exemplifies this with a seed-funded inbox-first API and features for multi-tenant agent inboxes. Established transactional providers (Postmark, Resend, Mailgun, SendGrid, Amazon SES, Mailtrap) remain strong for send-only use cases, while inbound and thread management distinguish newer entrants.