Hi @ABE1012
I have tested this now. Office 365 Group connector Send an HTTP won't work for this task

You need to use the outlook Send http action step.

Here is the flow you need

Above here are the details you needed
Under the Compose if you have multiple values use the single quotes around it.
'Developers','UAT'
The reason for this is if you want to map a single value and its in double quotes it won't bind it correctly if you using that value under the compose.
Here is my run history and test results

This is from my email

Hope it is useful and let me know how it goes.
Thanks