POST https://graph.microsoft.com/v1.0/me/messages/{id}/send
// Code snippets are only available for the latest version. Current version is 5.x
// To initialize your graphClient, see https://learn.microsoft.com/en-us/graph/sdks/create-client?from=snippets&tabs=csharp
await graphClient.Me.Messages["{message-id}"].Send.PostAsync();
// Code snippets are only available for the latest version. Current version is 6.x
GraphServiceClient graphClient = new GraphServiceClient(requestAdapter);
graphClient.me().messages().byMessageId("{message-id}").send().post();
<?php
use Microsoft\Graph\GraphServiceClient;
$graphServiceClient = new GraphServiceClient($tokenRequestContext, $scopes);
$graphServiceClient->me()->messages()->byMessageId('message-id')->send()->post()->wait();