通过Office365 C#使用Oauth2发送电子邮件

using System;
using System.Net.Http;
using System.Net.Http.Headers;
using System.Threading.Tasks;

public class Program
{
    public static async Task Main(string[] args)
    {
        string clientId = "YourClientId";
        string clientSecret = "YourClientSecret";
        string tenantId = "YourTenantId";
        string accessToken = await GetAccessToken(clientId, clientSecret, tenantId);

        string emailEndpoint = "https://graph.microsoft.com/v1.0/me/sendMail";
        string emailContent = "Your email content";
        string recipientEmail = "recipient@example.com";
        string senderEmail = "sender@example.com";
        string subject = "Your email subject";

        await SendEmail(accessToken, emailEndpoint, emailContent, recipientEmail, senderEmail, subject);
    }

    private static async Task<string> GetAccessToken(string clientId, string clientSecret, string tenantId)
    {
        string tokenEndpoint = $"https://login.microsoftonline.com/{tenantId}/oauth2/v2.0/token";
        string scope = "https://graph.microsoft.com/.default";

        using (HttpClient client = new HttpClient())
        {
            var requestContent = new FormUrlEncodedContent(new[]
            {
                new KeyValuePair<string, string>("grant_type", "client_credentials"),
                new KeyValuePair<string, string>("client_id", clientId),
                new KeyValuePair<string, string>("client_secret", clientSecret),
                new KeyValuePair<string, string>("scope", scope)
            });

            var response = await client.PostAsync(tokenEndpoint, requestContent);
            var responseContent = await response.Content.ReadAsStringAsync();

            // Parse the access token from the response
            // ...

            return accessToken;
        }
    }

    private static async Task SendEmail(string accessToken, string emailEndpoint, string emailContent, string recipientEmail, string senderEmail, string subject)
    {
        using (HttpClient client = new HttpClient())
        {
            client.DefaultRequestHeaders.Authorization = new AuthenticationHeaderValue("Bearer", accessToken);

            var email = new
            {
                message = new
                {
                    subject = subject,
                    body = new
                    {
                        contentType = "Text",
                        content = emailContent
                    },
                    toRecipients = new[]
                    {
                        new
                        {
                            emailAddress = new
                            {
                                address = recipientEmail
                            }
                        }
                    },
                    from = new
                    {
                        emailAddress = new
                        {
                            address = senderEmail
                        }
                    }
                }
            };

            var requestContent = new StringContent(JsonConvert.SerializeObject(email), Encoding.UTF8, "application/json");

            var response = await client.PostAsync(emailEndpoint, requestContent);
            var responseContent = await response.Content.ReadAsStringAsync();

            // Handle the response
            // ...
        }
    }
}