Send PM from different user - problem

Hi everyone.

I created a new non-sso user

Using these instructions I generated a session key for that user

Created a test endpoint with this code:

<#assign session_key = rest("/authentication/sessions/login?user.login=<new user login>&user.password=<new user password>").value/>
<#assign result_send = restadmin("/postoffice/notes/send?notes.recipient=/users/id/<my id>&notes.subject=test&notes.note=test&restapi.session_key=<freshly generated session key>")/>

I then opened that endpoint in an incognito window

The PM I received was from "anonymous", not from the new user.

What am I doing wrong?