The feature added in 2017 R2 was for authentication of the SOAP payload, not for managing headers within the payload. PI remains unusable as a secure source of data for Maximo without it because you can't configure a MAXAUTH header.
There's no way to configure headers for Notification Rules associated with a PI AF Services v2017 SP1 Elements with a SOAP or REST Web Service Endpoint. Authenticated web services, such as our company's Maximo's meter data inbound service requires a MAXAUTH header with a base64-encrypted username:password string. As a result, you can't use PI as a source of data for Maximo's condition-based maintenance triggers and automated asset meter reading updates, if Maximo uses authentication on its web services. That's a fairly common scenario with a high rate of return on the PI-Maximo integration efforts for a lot of customers.
ADMIN RESPONSE
Aug 20, 2022
HTTP headers for REST web service delivery end point was added in the PI AF 2018 SP2 release.
HTTP headers for SOAP web service delivery end point is currently in the backlog only.
In response to Cédric Vallée, "Hello, seems this is now available in th..."
Cedric: I don't see SOAP Headers enabled; can you clarify? What version of AF and PI Notifications?
Also see https://pisquare.osisoft.com/ideas/6026-soap-header-for-authentication
In response to Gopal Gopalkrishnan, "Cedric: I don't see SOAP Headers enabled..."
I read too fast :
This section lists features that were added in Release 2.10.5.9050 - 3/25/2019 of notifications.
Number
Description of Notifications Enhancement
150882
The web service delivery channel provides a way to specify additional http headers for a REST-based web service.