Hi virtualsue, you're right, I realize it was not clear in my original post. What I mean by "it does not work" is that no message is posted in the Zendesk to which I want to add a comment. The batch ends with no error. Messages returned by the post are similar whether the post succeeds or not (http 200 OK).
Thank you for pointing these 2 modules out hippo, I'll see if I can turn around the issue using them.