Hi Alice — wanted to follow up on...
\",\n});\n// That's it. If Alice replies, the agent never sees it.\n```\n\nThe 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.\n\n[Agent Accounts](https://developer.nylas.com/docs/v3/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.\n\nOutbound barely changes — it's still an API call. The new parts are everything transactional providers never gave you:\n\n| Concern | Transactional provider | Agent Account |\n|---|---|---|\n| Outbound | API call | Same — `POST /messages/send`\n|\n| Inbound | None (or polling a shared inbox) | Replies land automatically, fire `message.created`\n|\n| Threading | You track `Message-ID` yourself |\nHeaders preserved, threads grouped automatically |\n| Reply detection | Parse forwards, poll | Webhook within seconds of arrival |\n| DNS | SPF/DKIM/DMARC for the provider | MX, SPF, DKIM, DMARC for the mailbox host |\n\nOne call creates the account; the response includes a `grant_id`\n\nthat identifies it on every later request:\n\n```\ncurl --request POST \\\n --url \"https://api.us.nylas.com/v3/connect/custom\" \\\n --header \"Authorization: Bearer $NYLAS_API_KEY\" \\\n --header \"Content-Type: application/json\" \\\n --data '{\n \"provider\": \"nylas\",\n \"settings\": { \"email\": \"outreach@agents.yourcompany.com\" }\n }'\n```\n\n(Or `nylas agent account create outreach@agents.yourcompany.com`\n\nfrom the CLI.) Custom domains need MX and TXT records pointed at the mail host before inbound works — [provisioning docs here](https://developer.nylas.com/docs/v3/agent-accounts/provisioning/) — but a `*.nylas.email`\n\ntrial subdomain works instantly for prototyping.\n\nThe replacement send is nearly identical to what you had, with one addition that matters: store the `thread_id`\n\nfrom the response.\n\n``` js\nconst sent = await nylas.messages.send({\n identifier: AGENT_GRANT_ID,\n requestBody: {\n to: [{ email: \"prospect@example.com\", name: \"Alice\" }],\n subject: \"Following up on your demo request\",\n body: \"Hi Alice — wanted to follow up on...
\",\n },\n});\n\nawait db.conversations.create({\n threadId: sent.data.threadId,\n contactEmail: \"prospect@example.com\",\n step: \"awaiting_reply\",\n});\n```\n\nThat stored ID is how you'll recognize Alice's reply when it comes back.\n\nSubscribe a webhook to `message.created`\n\n— this is the entire piece of infrastructure your transactional setup never had:\n\n```\ncurl --request POST \\\n --url \"https://api.us.nylas.com/v3/webhooks\" \\\n --header \"Authorization: Bearer $NYLAS_API_KEY\" \\\n --header \"Content-Type: application/json\" \\\n --data '{\n \"trigger_types\": [\"message.created\"],\n \"webhook_url\": \"https://youragent.example.com/webhooks/nylas\"\n }'\n```\n\nThe notification fires within seconds of a reply arriving. The handler then closes the loop that didn't exist before: look up the thread, skip the agent's own outbound, fetch the full body, restore context.\n\n``` js\napp.post(\"/webhooks/nylas\", async (req, res) => {\n res.status(200).end();\n\n const event = req.body;\n if (event.type !== \"message.created\") return;\n\n const msg = event.data.object;\n if (msg.grant_id !== AGENT_GRANT_ID) return;\n\n // Skip the agent's own outbound messages.\n if (msg.from?.[0]?.email === \"outreach@agents.yourcompany.com\") return;\n\n // Is this a reply to something we sent?\n const conversation = await db.conversations.findByThreadId(msg.thread_id);\n if (!conversation) return; // new inbound, not a tracked reply\n\n // The webhook payload is a summary — fetch the full body.\n const full = await nylas.messages.find({\n identifier: AGENT_GRANT_ID,\n messageId: msg.id,\n });\n\n // Hand it to the LLM with conversation context restored.\n await processReply(full.data, conversation);\n});\n```\n\nWhen the agent answers, pass `reply_to_message_id`\n\nand the reply threads correctly in the recipient's client — Nylas sets the `In-Reply-To`\n\nand `References`\n\nheaders, so there's no `Message-ID`\n\nbookkeeping on your side. And the recipient sees a normal threaded reply: no \"sent via\" branding, no relay footer. The [reply-handling recipe](https://developer.nylas.com/docs/cookbook/agent-accounts/handle-replies/) has the full routing logic.\n\nIf your company's mail lives on Google Workspace or Microsoft 365, leave those MX records alone. The pattern that works:\n\n`yourcompany.com`\n\npointed where it is.`agents.yourcompany.com`\n\nand point This also isolates the agent's sender reputation from your primary domain — which you'll care about the first time an experiment goes sideways.\n\n**Does Nylas manage my conversation state too?** No — and the comparison table above is honest about this. The Threads API gives you conversation history for free, but the mapping from threads to your agent's workflow state (awaiting reply, confirmed, closed) is still yours to build. That's the `db.conversations`\n\ntable in the code above.\n\n**Do I still need to generate Message-ID values?** No. With a transactional provider, threading is your problem: you track\n\n`Message-ID`\n\nyourself and set `In-Reply-To`\n\non every send. With an Agent Account, headers are preserved and messages group into threads automatically — `reply_to_message_id`\n\nis the only threading concept your code touches.Keep the transactional provider for receipts and password resets if it's working — those flows don't need replies. Move only the conversations where the agent must see what comes back: outreach, support, scheduling, anything multi-turn. Different addresses, different jobs.\n\nThe complete walkthrough is in the [migration recipe](https://developer.nylas.com/docs/cookbook/agent-accounts/migrate-from-transactional-email/). Next step if you're tempted: provision a trial-subdomain account, re-point one send call at it, and reply to the email it sends you. Watching your own reply arrive as a webhook is the moment the architecture clicks.", "url": "https://wpnews.pro/news/migrating-from-transactional-email-to-agent-accounts", "canonical_source": "https://dev.to/qasim157/migrating-from-transactional-email-to-agent-accounts-5775", "published_at": "2026-06-12 12:38:07+00:00", "updated_at": "2026-06-12 12:41:41.510879+00:00", "lang": "en", "topics": ["ai-agents", "ai-products", "ai-tools", "ai-infrastructure", "ai-startups"], "entities": ["Nylas", "SendGrid", "Resend", "Postmark", "Agent Accounts"], "alternates": {"html": "https://wpnews.pro/news/migrating-from-transactional-email-to-agent-accounts", "markdown": "https://wpnews.pro/news/migrating-from-transactional-email-to-agent-accounts.md", "text": "https://wpnews.pro/news/migrating-from-transactional-email-to-agent-accounts.txt", "jsonld": "https://wpnews.pro/news/migrating-from-transactional-email-to-agent-accounts.jsonld"}}