Send and receive in one provider — no Zoho Mail and IMAP bolted on to read a reply.

// OUT — ZeptoMail send. Zoho-enczapikey token, nested to[].email_address.
await fetch("https://api.zeptomail.com/v1.1/email", {
  method: "POST",
  headers: { Authorization: `Zoho-enczapikey ${ZEPTO_SEND_TOKEN}` },
  body: JSON.stringify({
    from: { address: "agent@yourco.dev" },
    to: [{ email_address: { address: replyTo } }],
    subject: `Re: ${subject}`,
    htmlbody: answer.html,   // no inReplyTo/threading helper
  }),
});

// IN — ZeptoMail can't receive. Bolt on Zoho Mail, poll over IMAP:
const imap = new ImapFlow({
  host: "imap.zoho.com", port: 993, secure: true,
  auth: { user: "agent@yourco.dev", pass: ZOHO_APP_PASSWORD },
});
await imap.connect();
await imap.mailboxOpen("INBOX");
for await (const msg of imap.fetch({ seen: false }, { source: true })) {
  const mail = await simpleParser(msg.source);   // MIME → fields is yours
  // dedupe, mark \Seen atomically, verify SPF/DKIM/DMARC: also yours
}

POST /your-webhook   Content-Type: application/json
x-mailkite-signature: t=…,v1=…   (HMAC-SHA256 — verify locally)

{
  "id": "msg_2Hk9…",
  "type": "email.received",
  "from": { "address": "ada@example.com" },
  "to": [{ "address": "support@myapp.ai" }],
  "subject": "Re: invoice #1042",
  "text": "Looks good — approved!",
  "html": "<p>Looks good — approved!</p>",
  "threadId": "<a1b2c3@mail.example.com>",
  "auth": { "spf": "pass", "dkim": "pass", "dmarc": "pass", "spam": "ham" },
  "attachments": [
    { "filename": "po.pdf", "contentType": "application/pdf",
      "size": 18213, "url": "https://api.mailkite.dev/att/2Hk9…/0?sig=…" }
  ]
}