How can I activate asynchronous notifications for a specific email?
To get asynchronous notifications for a specific email, send the email using the API or the SMTP interface:
If using the API, set the envid value in Responses corresponding to the value of the message field env_id which is returned to the message queue by asynchronous notifications.
If using the SMTP interface, use either of the following methods:
Set the message_id in the header. The field value corresponds to the message field msg_id value returned to the message queue by asynchronous notifications.
Run the data command. The returned value contains envid value, for example, queued as freedom ###envid=256790474, which corresponds to the value of the message field env_id returned to the message queue by asynchronous notifications.