Migrating From Transactional Email to Agent Accounts

This is what most agent email code looks like today: // SendGrid / Resend / Postmark — outbound only await sendgrid . send ({ to : " prospect@example.com " , from : " outreach@yourcompany.com " , subject : " Following up on your demo request " , html : " <p>Hi Alice — wanted to follow up on...</p> " , }); // That's it. If Alice replies, the agent never sees it. The send works fine. The problem is everything after: when Alice replies, that reply bounces, lands at a no-reply nobody reads, or hits a human inbox the agent can't reach programmatically. The agent is talking into a void. Transactional providers were built for receipts and password resets — one-way mail — and an agent that's supposed to hold a conversation needs a receive path those APIs simply don't have. Agent Accounts (a beta feature from Nylas) close that gap with a full hosted mailbox: send and receive, with threading, webhooks, and folders built in. Here's what the migration actually involves. The delta, honestly Outbound barely changes — it's still an API call. The new parts are everything transactional providers never gave you: Concern Transactional provider Agent Account Outbound API call Same — POST /messages/send Inbound None (or polling a shared inbox) Replies land automatically, fire message.created Threading You track Message-ID yourself Headers preserved, threads grouped automatically Reply detection Parse forwards, poll Webhook within seconds of arrival DNS SPF/DKIM/DMARC for the provider MX, SPF, DKIM, DMARC for the mailbox host Provision the mailbox One call creates the account; the response includes a grant_id that identifies it on every later request: curl --request POST \ --url "https://api.us.nylas.com/v3/connect/custom" \ --header "Authorization: Bearer $NYLAS_API_KEY " \ --header "Content-Type: application/json" \ --data '{ "provider": "nylas", "settings": { "email": "outreach@agents.yourcompany.com" } }' (Or nylas agent account create outreach@agents.yourcompany.com from the CLI.) C