为了让它工作，我必须启用我的gmail帐户，以便其他应用程序可以访问它。这是通过“启用不太安全的应用程序”来完成的，也可以使用这个链接: https://accounts.google.com/b/0/DisplayUnlockCaptcha

我也遇到了同样的问题，但通过gmail的安全设置和允许不太安全的应用程序解决了。 Domenic & Donny的代码有效，但前提是你启用了该设置

如果您已登录(到谷歌)，您可以按照此链接并切换“打开”以“访问不太安全的应用程序”

在Gmail / Outlook.com邮箱更改发件人:

为了防止欺骗- Gmail/Outlook.com不会让你从任意用户帐户名发送。

如果发件人数量有限，则可以按照以下说明将From字段设置为此地址:从不同地址发送邮件

如果你想从一个任意的电子邮件地址发送(比如用户在网站上输入他们的电子邮件，而你不希望他们直接给你发送电子邮件)，你能做的最好的是:

        msg.ReplyToList.Add(new System.Net.Mail.MailAddress(email, friendlyName));

这可以让你在电子邮件账户中点击“回复”，在反馈页面上回复你乐队的粉丝，但他们不会收到你的实际电子邮件，这可能会导致大量垃圾邮件。

如果你在一个受控制的环境中，这工作得很好，但请注意，我看到一些电子邮件客户端发送到from地址，即使回复指定(我不知道是哪个)。

使用这种方式

MailMessage sendmsg = new MailMessage(SendersAddress, ReceiversAddress, subject, body); 
SmtpClient client = new SmtpClient("smtp.gmail.com");

client.Port = Convert.ToInt32("587");
client.EnableSsl = true;
client.Credentials = new System.Net.NetworkCredential("mail-id@gmail.com","MyPassWord");
client.Send(sendmsg);

别忘了这一点:

using System.Net;
using System.Net.Mail;

在谷歌更新后，这是使用c#或。net发送电子邮件的有效方法。

using System;
using System.Net;
using System.Net.Mail;

namespace EmailApp
{
    internal class Program
    {
        public static void Main(string[] args)
        {
            String SendMailFrom = "Sender Email";
            String SendMailTo = "Reciever Email";
            String SendMailSubject = "Email Subject";
            String SendMailBody = "Email Body";

            try
            {
                SmtpClient SmtpServer = new SmtpClient("smtp.gmail.com",587);
                SmtpServer.DeliveryMethod = SmtpDeliveryMethod.Network;
                MailMessage email = new MailMessage();
                // START
                email.From = new MailAddress(SendMailFrom);
                email.To.Add(SendMailTo);
                email.CC.Add(SendMailFrom);
                email.Subject = SendMailSubject;
                email.Body = SendMailBody;
                //END
                SmtpServer.Timeout = 5000;
                SmtpServer.EnableSsl = true;
                SmtpServer.UseDefaultCredentials = false;
                SmtpServer.Credentials = new NetworkCredential(SendMailFrom, "Google App Password");
                SmtpServer.Send(email);

                Console.WriteLine("Email Successfully Sent");
                Console.ReadKey();
            }
            catch (Exception ex)
            {
                Console.WriteLine(ex.ToString());
                Console.ReadKey();
            }

        }
    }
}

要创建应用程序密码，您可以按照这篇文章: https://www.techaeblogs.live/2022/06/how-to-send-email-using-gmail.html

下面是一个从web.config发送邮件和获取凭证的方法:

public static string SendEmail(string To, string Subject, string Msg, bool bodyHtml = false, bool test = false, Stream AttachmentStream = null, string AttachmentType = null, string AttachmentFileName = null)
{
    try
    {
        System.Net.Mail.MailMessage newMsg = new System.Net.Mail.MailMessage(System.Configuration.ConfigurationManager.AppSettings["mailCfg"], To, Subject, Msg);
        newMsg.BodyEncoding = System.Text.Encoding.UTF8;
        newMsg.HeadersEncoding = System.Text.Encoding.UTF8;
        newMsg.SubjectEncoding = System.Text.Encoding.UTF8;

        System.Net.Mail.SmtpClient smtpClient = new System.Net.Mail.SmtpClient();
        if (AttachmentStream != null && AttachmentType != null && AttachmentFileName != null)
        {
            System.Net.Mail.Attachment attachment = new System.Net.Mail.Attachment(AttachmentStream, AttachmentFileName);
            System.Net.Mime.ContentDisposition disposition = attachment.ContentDisposition;
            disposition.FileName = AttachmentFileName;
            disposition.DispositionType = System.Net.Mime.DispositionTypeNames.Attachment;

            newMsg.Attachments.Add(attachment);
        }
        if (test)
        {
            smtpClient.PickupDirectoryLocation = "C:\\TestEmail";
            smtpClient.DeliveryMethod = System.Net.Mail.SmtpDeliveryMethod.SpecifiedPickupDirectory;
        }
        else
        {
            //smtpClient.EnableSsl = true;
        }

        newMsg.IsBodyHtml = bodyHtml;
        smtpClient.Send(newMsg);
        return SENT_OK;
    }
    catch (Exception ex)
    {

        return "Error: " + ex.Message
             + "<br/><br/>Inner Exception: "
             + ex.InnerException;
    }

}

以及web.config中相应的部分:

<appSettings>
    <add key="mailCfg" value="yourmail@example.com"/>
</appSettings>
<system.net>
  <mailSettings>
    <smtp deliveryMethod="Network" from="yourmail@example.com">
      <network defaultCredentials="false" host="mail.exapmple.com" userName="yourmail@example.com" password="your_password" port="25"/>
    </smtp>
  </mailSettings>
</system.net>