Send a message in a chat

POSThttps://api.postpress.ai/v1/chats/{chat_id}/messages

Send a message to a chat with optional attachments. The body is sent as `multipart/form-data` so binary fields (`voice_message`, `video_message`, `attachments[]`) can be uploaded alongside text fields.

Authorization

X-API-KEYstringrequired

API key from your postpress dashboard. Sent as a request header.

Path parameters

chat_idstringrequired

The id of the chat to post the message in.

Request body (multipart/form-data)

textstring

Message text body.

account_idstring

Restrict sending to a specific postpress account so requests cannot leak across accounts.

thread_idstring

Slack only. The id of the thread to reply into.

quote_idstring

The id of an existing message to quote or reply to.

voice_messagestring (binary)

LinkedIn or WhatsApp only. Audio file to send as a voice message. WhatsApp prefers `.mp3`/`.m4a`; LinkedIn prefers `.m4a`. For Instagram and Telegram, use `attachments` instead.

video_messagestring (binary)

LinkedIn only. Video file to send as a video message. On WhatsApp, use `attachments` instead.

attachmentsarray of string (binary)

Files to attach to the message.

attachments array

<file>string (binary)

typing_durationstring

WhatsApp only. Duration in milliseconds to simulate a typing indicator before the message is sent.

Response 201 Created

objectstringMessageSentrequired

message_idstringrequired

The postpress id of the newly sent message. Nullable when the provider does not return one synchronously.

Example request

curl --request POST \
  --url 'https://api.postpress.ai/api/v1/chats/chat_01HXYZ4QK3WJ8FN3M6QH7TZ8GR/messages' \
  --header 'X-API-KEY: pp_live_...' \
  --header 'accept: application/json' \
  --header 'content-type: multipart/form-data' \
  --form 'text=Got it - thanks!' \
  --form 'attachments=@/path/to/file.pdf'

Example response

{
  "object": "MessageSent",
  "message_id": "msg_01HXYZ4QK3WJ8FN3M6QH7TZ8GR"
}

Errors

Every error response follows the same envelope:

titlestringrequired

Short error title.

detailstringoptional

Human-readable explanation.

instancestringoptional

Request identifier for support.

typestringrequired

Error type identifier.

statusnumberrequired

HTTP status code.

401 Unauthorized13 types

Credentials are missing, expired, or otherwise invalid.

errors/missing_credentials - Some credentials are necessary to perform the request.
errors/multiple_sessions - LinkedIn limits multiple sessions on certain Recruiter accounts. Use the cookie connection method.
errors/invalid_checkpoint_solution - The checkpoint resolution did not pass successfully. Retry.
errors/invalid_proxy_credentials - The provided proxy credentials are invalid.
errors/checkpoint_error - The checkpoint does not appear to be resolvable.
errors/invalid_credentials - The provided credentials are invalid.
errors/expired_credentials - Credentials have expired. Reconnect the account.
errors/insufficient_privileges - This resource is out of your API-key scopes.
errors/disconnected_account - The account is disconnected from the provider service.
errors/disconnected_feature - The service you're trying to reach is disconnected.
errors/invalid_credentials_but_valid_account_imap - IMAP/SMTP credentials are invalid but the account is otherwise valid.
errors/expired_link - This link has expired. Generate a new one.
errors/wrong_account - The provided credentials do not match the correct account.

403 Forbidden9 types

Authenticated but the account is restricted or the action is not allowed.

errors/account_restricted - The account has been restricted by the provider.
errors/account_mismatch - This action cannot be done with your account.
errors/insufficient_permissions - Valid authentication but insufficient permissions to perform the request.
errors/session_mismatch - Token user id does not match client session id.
errors/feature_not_subscribed - The requested feature has not been subscribed or authenticated properly.
errors/subscription_required - A subscription is required to use this feature.
errors/unknown_authentication_context - An additional step seems necessary to complete login.
errors/action_required - An additional step is required.
errors/resource_access_restricted - You don't have access to this resource.

404 Not Found2 types

Account, chat, thread, or provider resource not found.

errors/resource_not_found - The requested resource was not found.
errors/invalid_resource_identifier - The provided identifier is not valid.

415 Unsupported Media Type1 types

The provider rejected one or more of the attached media.

errors/unsupported_media_type - The media format is not supported by the provider.

422 Unprocessable Entity35 types

The message could not be sent because of provider-side validation.

errors/invalid_account - The account cannot perform this action.
errors/invalid_recipient - The recipient is invalid for this provider.
errors/no_connection_with_recipient - A connection with the recipient is required.
errors/blocked_recipient - The recipient has blocked the sender.
errors/user_unreachable - The recipient cannot be reached.
errors/unprocessable_entity - The provider could not process the message.
errors/payment_error - A payment is required to send this message.
errors/action_already_performed - The action was already performed.
errors/invalid_message - The message body or attachments are invalid.
errors/invalid_post - The referenced post is invalid.
errors/not_allowed_inmail - InMail is not allowed for this recipient.
errors/insufficient_credits - Not enough credits to send this message.
errors/cannot_resend_yet - The message cannot be re-sent yet.
errors/cannot_resend_within_24hrs - The message cannot be re-sent within 24 hours.
errors/limit_exceeded - The provider's sending limit was exceeded.
errors/already_invited_recently - The recipient was already invited recently.
errors/already_connected - Already connected with this recipient.
errors/cannot_invite_attendee - This attendee cannot be invited.
errors/parent_mail_not_found - Parent email was not found.
errors/parent_mail_invalid_provider_id - Parent email has an invalid provider id.
errors/invalid_reply_subject - The reply subject is invalid.
errors/invalid_headers - The message headers are invalid.
errors/send_as_denied - The provider denied the send-as request.
errors/invalid_folder - The target folder is invalid.
errors/invalid_thread - The target thread is invalid.
errors/unauthorized - The provider rejected the request as unauthorized.
errors/sender_rejected - The sender was rejected by the provider.
errors/recipient_rejected - The recipient was rejected by the provider.
errors/ip_rejected_by_server - The sending IP was rejected by the upstream server.
errors/provider_unreachable - The provider is currently unreachable.
errors/account_configuration_error - The account is misconfigured.
errors/cant_send_message - The message could not be sent.
errors/realtime_client_not_initialized - The realtime client is not initialized.
errors/comments_disabled - Comments are disabled on this resource.
errors/insufficient_job_slot - No remaining job slot to send this message.

429 Too Many Requests1 types

The provider is rate-limiting this account. Retry later.

errors/too_many_requests - The provider cannot accept any more requests at the moment.

500 Internal Server Error3 types

Something went wrong on our side or with the upstream provider.

errors/unexpected_error - Something went wrong.
errors/provider_error - The provider is experiencing operational problems. Retry later.
errors/authentication_intent_error - The current authentication intent was killed after failure.

503 Service Unavailable5 types

postpress is temporarily unable to handle the request.

errors/no_client_session - No client session is currently running.
errors/no_channel - No channel to client session.
errors/no_handler - Handler missing for that request.
errors/network_down - Network is down on the server side. Retry shortly.
errors/service_unavailable - Service temporarily unavailable. Retry later.

504 Gateway Timeout1 types

The upstream provider did not respond in time.

errors/request_timeout - Request timed out. Retry, and contact support if it persists.

Updated May 2026