6.4. Payload format

Below is a description of the payload format used for the rewritten URL:s and tracking pixels. This is only relevant if you want to implement a custom tracking service rather than the one we provide, otherwise, see the events section.

The payload format is a base64url encoded string where:

• The first byte is the tracking.secret.id.

• The next 32 bytes is a HMAC SHA-256 hash of the tracking data using the tracking.secret.key.

• All the bytes after this is for the tracking data which is a JSON object compressed using zlib DEFLATE (without an appended zlib header) in the following format:

{
    "r": "[email protected]",
    "m": "<36e76ce2-b5a6-11ec-b8dd-000c292d8854@c568c9a1654f>",
    "u": "http://example.com/example/path",
    "a": {}
}

Note

We also have a HSL module if you want to implement engagement tracking during SMTP submission as well.