Issue in sending personal message in MS Teams with Graph API

I registered my application in Azure AD website and collected the tenant ID, client ID, and client secret. I was able to generate the access token and chat ID for personal messaging which is requested in the below format

{
    "chatType": "oneOnOne",
    "members": [
        {
            "@odata.type": "#microsoft.graph.aadUserConversationMember",
            "roles": [
                "owner"
            ],
            "user@odata.bind": "https://graph.microsoft.com/v1.0/users('{your-user-id}')"
        },
        {
            "@odata.type": "#microsoft.graph.aadUserConversationMember",
            "roles": [
                "owner"
            ],
            "user@odata.bind": "https://graph.microsoft.com/v1.0/users('{user-id}')"
        }
    ]
}

I was able to generate chat ID for the mail. However when I tried the below end point

https://graph.microsoft.com/v1.0/chats/%7Bchat_id%7D/messages

for sending the message I am getting an error as below

{
    "error": {
        "code": "Unauthorized",
        "message": "Message POST is allowed in application-only context only for import purposes. Refer to https://docs.microsoft.com/microsoftteams/platform/graph-api/import-messages/import-external-messages-to-teams for more details.",
        "innerError": {
            "date": "2024-06-10T05:06:10",
            "request-id": "4b1bf353-d1c0-4852-afcc-0c508d76d6d3",
            "client-request-id": "4b1bf353-d1c0-4852-afcc-0c508d76d6d3"
        }
    }
}

Why am I getting this error?

I am expecting the token generated from application registration credentials to send personal messages in teams. However I am facing this issue. Now I am able to generate chat ID with any two user mail IDs in my organization. But I am blocked from sending personal Teams messages.

As mentioned in the MS Doc, sending messages with application permission are only supported for migration. So, it's not possible to send teams message with Application permissions.

Initially, I too got same error when I tried to send message with token generated with client credentials flow:

POST https://graph.microsoft.com/v1.0/chats/chatID/messages
Content-type: application/json

{
  "body": {
     "content": "Hello world"
  }
}

Response:

To resolve the error, switch to delegated flows like authorization code flow for generating access token.

In my case, I added ChatMessage.Send permission of Delegated type in my application like this:

Now, I ran below authorization request in browser that gives code value in address bar after successful authentication:

https://login.microsoftonline.com/tenantId/oauth2/v2.0/authorize
?client_id=appId
&response_type=code
&redirect_uri=https://jwt.ms
&response_mode=query
&scope=ChatMessage.Send
&state=12345

You can use this code value to get access token using authorization code flow via Postman with below parameters:

POST https://login.microsoftonline.com/tenantId/oauth2/v2.0/token
grant_type:authorization_code
client_id:appId
client_secret:secret
scope:ChatMessage.Send
code:code
redirect_uri:https://jwt.ms

Response:

When I used this token to send message in chat, I got the response successfully like this:

POST https://graph.microsoft.com/v1.0/chats/chatID/messages
Content-type: application/json

{
  "body": {
     "content": "Hello world"
  }
}

Response: