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Reply to a message in one call. Drin threads it for you: From defaults to the parent’s inbox, To to the parent’s sender, the subject gets a Re: prefix, and the In-Reply-To / References headers are set. POST /v1/emails/{id}/reply Reply to an inbound message and the new message lands in the same thread on the recipient’s side. The body is optional — every field below has a sensible default derived from the parent message. At minimum, supply html or text.

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Path parameters

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id
string
required
The id of the message you’re replying to (typically an inbound message).

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Body parameters

The entire body is optional; pass only what you want to override.
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html
string
The HTML reply body. Provide html, text, or both.
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text
string
The plain-text reply body.
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subject
string
Override the subject. Defaults to the parent’s subject with a Re: prefix.
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from
object
Override the sender, { email, name? }. Defaults to the parent’s inbox address so threading stays intact.

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Headers

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Idempotency-Key
header
Make the reply safe to retry — the same key replays the original result for 24 hours. See Idempotency & retries.

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Request

curl https://api.drin.run/v1/emails/msg_01HZX9K3T2QF7P0M4N8B6C5D/reply \
  -H "Authorization: Bearer $DRIN_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "html": "<p>Thanks for reaching out — we are on it.</p>",
    "text": "Thanks for reaching out — we are on it."
  }'

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Response

202 Accepted — the reply was queued. The response is the same shape as a send: the new message’s id and status.
202 Accepted
{
  "id": "msg_01HZXB7Q4R2KD9F0M1N3P5T8",
  "status": "queued"
}
See the whole conversation. To read both sides of a thread joined together, use GET /v1/threads/{id}. The guide on replying in-thread walks the full receive-then-reply loop.