Send Email

POST

/onebox/send

Send a new email, or reply inside an existing thread, from a connected mailbox.

Sends through the mailbox named in account, so the message leaves from that address and appears in its Sent folder.

Sending a reply

Pass both threadId and messageId from the message being replied to. Without them the message starts a new thread. Supply body for HTML or text for plain text; sending both lets the client pick.

This endpoint delivers real mail to real recipients. There is no sandbox mode.

Example

{
  "userId": "K5PF9Y068AMDGENV5BTCNJJZK55F",
  "account": "andrew.lawyer@aurumlawyer.com",
  "to": "client@example.com",
  "subject": "Following up",
  "body": "<p>Just checking in on the proposal.</p>"
}

Request

Authorization

API Key

Add parameter in header

cmr-x-api-key

Example:

cmr-x-api-key: ********************

Body Params application/jsonRequired

Examples

Responses

🟢200Success

application/json

Message accepted for delivery. The data object is passed through from the mail backend.

Bodyapplication/json

🟠401Unauthorized

🟠404Not Found

🟠422Validation Error

Request Example

Shell

JavaScript

Java

Swift

curl --location 'https://customers.coldmailreseller.com/api/v1/integration/onebox/send' \
--header 'cmr-x-api-key: <api-key>' \
--header 'Content-Type: application/json' \
--data-raw '{
    "userId": "K5PF9Y068AMDGENV5BTCNJJZK55F",
    "account": "andrew.lawyer@aurumlawyer.com",
    "to": "client@example.com",
    "subject": "Following up",
    "body": "<p>Just checking in on the proposal.</p>",
    "text": "Just checking in on the proposal.",
    "cc": [
        "colleague@example.com"
    ],
    "bcc": [
        "archive@example.com"
    ],
    "threadId": "1877937258181177440",
    "messageId": "<Gq3K93hRllxHkWlnjYO1wg@notifications.google.com>"
}'

Response Example

200 - Example 1

{
    "status": 200,
    "message": "Email sent",
    "data": {}
}

Modified at 2026-10-02 12:23:15

Delete Label

Disconnect Mailbox

Send Email

Sending a reply#

Example#

Request

Responses

Sending a reply

Example