I am trying to update the subject of an email using Power Automate. The flow is triggered by the email being received in a shared mailbox, it does a bunch of things and then I have a compose action to take the email subject and add a reference number to it, it's just a string, that's working fine. Then there is an Outlook connector "Send an HTTP request", which is very simple, but it doesn't seem to be carrying the correct headers through, Content-Length is missing.
Here is the workflow Send an HTTP request step:
The expression in the compose action:
Raw inputs once I test the workflow:
The MessageID was a bit long, so I scrolled over a bit, but you can see the dynamic content is working and the URI seems fine, but the Content-Length header is missing.
And the raw outputs as well, in case that is helpful:
That really was too long, so I copied it to Word before taking the screenshot.
It seems like it should be pretty straightforward, I'm not sure why it isn't working. Is what I am trying to do not possible with the Outlook connector, maybe? I can't use any other HTTP connecters, it says it's a premium feature not included in my licence. If it's not possible in Power Automate, I might be able to sort something out with an Outlook macro instead, but I'm not great with those so I'd rather not.
