The Unibox API exposes canonical lead email conversations so connected tools can review chronological messages, understand current answer status, filter by reply classification, and send validated plaintext replies from mailbox identities in your workspace.
Filter by answer status, campaign, mailbox, conversation classification, reply primary category, and detailed reply subcategory.
Answer status mirrors the current Unibox behavior so API clients and the web inbox stay aligned.
Replies require a current latest-message check, idempotency key, workspace sender validation, and plaintext content validation before sending.
All requests use your Organization API Key with the standard bearer token header.
reply_context.expected_latest_message_id from the list or detail response when calling POST /api/v1/unibox/threads/{thread_id}/reply.from_address to use the Unibox default sender for the thread. If you provide one, it must be an active sender mailbox in the same workspace.body_text only. Simple Unicode text is supported for multilingual replies, but HTML, attachments, emoji, and unsupported control characters are rejected.idempotency_key in the JSON body or an Idempotency-Key header. Reusing the same key with the same request returns the original send response; reusing it with different content returns a conflict.Reply sends return clear HTTP 429 details when limited. Current limits are 10 replies per API key per minute, 30 replies per workspace per minute, 10 replies per sender mailbox per minute, and 1 reply per thread per 30 seconds.