Inbox

iMessage conversations live in the unified inbox. Sending is the same POST /v1/inbox/conversations/{conversationId}/messages call as every other channel, with accountId set to the sender's account; iMessage adds a few fields of its own.

What you can send

subject, effect, contactCard and channel are accepted on the JSON body only and return 400 on other platforms.

Edit and unsend

An outbound message can be edited within 15 minutes and unsent within 2 minutes of sending, Apple's own limits. PATCH …/messages/{messageId} with text edits it and keeps the edit history on the stored message; DELETE …/messages/{messageId} unsends it and leaves a tombstone. Outside the window the calls return 409 with edit_window_expired or unsend_window_expired.

Reactions

Apple's six tapbacks (❤️ 👍 👎 😂 ‼️ ❓) render natively; any other emoji is sent as a custom emoji tapback, which iOS 18 and later display. Inbound reactions arrive on the reaction.received webhook and on the message's reactions, keyed per reactor, with the attachment index when the reaction targeted one attachment of a multi-attachment message. See Add message reaction.

What you receive

Inbound messages fire message.received and carry, in metadata, the channel the message arrived on, the message type (text, audio, attachments, sticker, location), the reply thread id, a detected language code, the transcript of a voice message, and any rich-text markup as markdownText. A shared location or sticker arrives without coordinates; a Maps link in the text is parsed into a location when present. A FaceTime call attempt shows up in the thread as a call-typed message. Inbound media is copied to Zernio storage so the URLs outlive the provider's retention.

Delivery follows message.delivered and message.failed; a send the provider defers to respect sending intervals sits at queued until it goes out.

Group chats

Group threads arrive on their own conversation with isGroup: true; replying uses the normal send call. GET /v1/imessage/groups/{conversationId} returns the participants, PATCH renames the group or changes its photo, and POST / DELETE …/participants add and remove people. Starting a group from a sender is POST /v1/imessage/groups: it is asynchronous, so the thread appears on the first group webhook. Group writes are applied by the provider in the background; a 200 means accepted.

Messaging new contacts

A sender you order through Zernio can start a conversation with someone who never wrote to it, through POST /v1/inbox/conversations or New message in the dashboard. The first message is an introduction (cold outreach is fine; no links, emails, phone numbers, prices or attachments), new conversations are paced and warmed up per sender, and until the contact replies you can follow up at most twice, a day apart. See New Contacts for the full rules.

Contacts who wrote to you within the last day can be replied to without any interval. Messages to contacts who have not written in the last 24 hours are spaced at least 2 minutes apart per sender (429 with new_contact_limit inside that window). A send to a contact who has opted out returns 409 with recipient_opted_out; see Opt-in & Audience.