Sending a message in a Teams channel using a fictitious user via Microsoft Graph API

[DiegoL93]

Hi everyone,

I have the following requirement:

I have created a fictitious user to send a message in a Teams channel, a sort of alert.

I am able to log in to Graph Explorer with this user and by using the following Graph API call https://graph.microsoft.com/beta/teams/{group_id}/channels/{channel_id}/messages I can send a message inside the Microsoft Teams channel.

Now, my question is: how can I insert a message into the Channel from "outside" Graph Explorer, without direct login in with the user, for example using a Postman request? I am positive that I have all the necessary information, like client IDs, tokens, etc. 

Since I am by no means an expert in Microsoft Graph or API calls, I'm kindly asking for your help.

Thanks in advance and kind regards,

Diego

[#2]

The only way so far I have been able to do is via Power Automate.
Follow the steps here and it *WILL* work.
https://www.c-sharpcorner.com/article/sending-teams-message-to-any-user-from-a-specific-user-from-po...

[#3]

Similar to Terry Wells’ example, if you’re posting to a channel, you can log into Power Automate with your fictitious user and create a flow to post a message to the channel - https://learn.microsoft.com/en-us/power-automate/teams/send-a-message-in-teams#posting-a-message-as-...