Answer:Utilize the session ID contained within the outbound message notification as the authorization header.
Utilize the Enterprise WSDL login() operation to obtain a new session ID.
Utilize the REST API login() operation to obtain a new session ID.
Explanation:
For the authorization we can utilize the session I in the outbound message notification
Then, we can obtain new session IDs using WSDL login() to exchange information via http and smtp.
For integrating APIs we can utilize the REST API login()to obtain session IDs.