修复使用 Gmail API 的自定义域电子邮件的“邮件客户端未启用”错误

通过 Gmail API 解决自定义域电子邮件的“邮件客户端未启用”问题

使用 C# 和 Gmail API 以及 OAuth2 进行身份验证和电子邮件发送的后端解决方案

using Google.Apis.Auth.OAuth2;
using Google.Apis.Gmail.v1;
using Google.Apis.Gmail.v1.Data;
using Google.Apis.Services;
using MimeKit;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Net.Mail;
namespace GmailAPIExample
{
    public class GmailServiceHandler
    {
        public string SendEmail(string accessToken, string from, List<string> recipients, string subject, string body)
        {
            try
            {
                // Initialize credentials
                var credential = GoogleCredential.FromAccessToken(accessToken).CreateScoped(GmailService.Scope.GmailSend);
                var service = new GmailService(new BaseClientService.Initializer
                {
                    HttpClientInitializer = credential,
                    ApplicationName = "YourAppName"
                });
                // Construct MimeMessage
                var message = new MimeMessage();
                message.From.Add(new MailboxAddress("Sender Name", from));
                foreach (var recipient in recipients)
                {
                    message.To.Add(new MailboxAddress("", recipient));
                }
                message.Subject = subject;
                message.Body = new TextPart("html") { Text = body };
                // Encode message
                var encodedMessage = Convert.ToBase64String(System.Text.Encoding.UTF8.GetBytes(message.ToString()));
                var gmailMessage = new Message { Raw = encodedMessage.Replace("+", "-").Replace("/", "_").Replace("=", "") };
                // Send email
                var request = service.Users.Messages.Send(gmailMessage, "me");
                var response = request.Execute();
                return $"Email sent successfully. Message ID: {response.Id}";
            }
            catch (Exception ex)
            {
                return $"Error sending email: {ex.Message}";
            }
        }
    }
}

替代方案：使用 OAuth2 的 Gmail API 的 Python 脚本

使用 Python、Gmail API 和 google-auth 库进行令牌管理和电子邮件发送的后端解决方案

from google.oauth2.credentials import Credentials
from googleapiclient.discovery import build
import base64
from email.mime.text import MIMEText
def send_email(access_token, sender, recipients, subject, body):
    try:
        # Authenticate the Gmail API
        creds = Credentials(access_token)
        service = build('gmail', 'v1', credentials=creds)
        # Create MIME message
        message = MIMEText(body, 'html')
        message['to'] = ', '.join(recipients)
        message['from'] = sender
        message['subject'] = subject
        raw_message = base64.urlsafe_b64encode(message.as_string().encode('utf-8')).decode('utf-8')
        # Send email
        message_body = {'raw': raw_message}
        sent_message = service.users().messages().send(userId='me', body=message_body).execute()
        return f"Email sent successfully. Message ID: {sent_message['id']}"
    except Exception as e:
        return f"An error occurred: {str(e)}"

1. 有关 Gmail API 功能和身份验证的详细信息来自官方 Google 开发人员文档。了解更多信息，请访问 Gmail API 文档 。
2. 有关处理 Gmail API 的 OAuth 2.0 的信息引用自 Google 的 OAuth 2.0 指南。探索它在 OAuth 2.0 指南 。
3. 对 SPF 和 DKIM 等电子邮件身份验证协议的见解源自 DMARC.org 。
4. 有关 Gmail API 错误故障排除的指南取自社区论坛和文章： 堆栈溢出 。