Как отправить письмо в ASP.NET C#

Я очень новичок в области ASP.NET C#. Я планирую отправить письмо через ASP.NET C#, и это SMTP- адрес от моего провайдера:

smtp-proxy.tm.net.my

Ниже то, что я пытался сделать, но не получилось.

<%@ Page Language="C#" AutoEventWireup="true" CodeFile="Default.aspx.cs" Inherits="SendMail" %>
<html>
<head id="Head1" runat="server"><title>Email Test Page</title></head>
<body>
    <form id="form1" runat="server">
        Message to: <asp:TextBox ID="txtTo" runat="server" /><br>
        Message from: <asp:TextBox ID="txtFrom" runat="server" /><br>
        Subject: <asp:TextBox ID="txtSubject" runat="server" /><br>
        Message Body:<br>
        <asp:TextBox ID="txtBody" runat="server" Height="171px" TextMode="MultiLine"  Width="270px" /><br>
        <asp:Button ID="Btn_SendMail" runat="server" onclick="Btn_SendMail_Click" Text="Send Email" /><br>
        <asp:Label ID="Label1" runat="server" Text="Label"></asp:Label>
    </form>
</body>
</html>

И ниже мой код позади:

using System;
using System.Web.UI.WebControls;
using System.Net.Mail;
public partial class SendMail : System.Web.UI.Page
{
    protected void Btn_SendMail_Click(object sender, EventArgs e)
    {
        MailMessage mailObj = new MailMessage(
            txtFrom.Text, txtTo.Text, txtSubject.Text, txtBody.Text);
        SmtpClient SMTPServer = new SmtpClient("127.0.0.1");
        try
        {
            SMTPServer.Send(mailObj);
        }
        catch (Exception ex)
        {
            Label1.Text = ex.ToString();
        }
    }
}

PS: Мне жаль, что я не мог понять концепцию SMTP получателя / отправителя, и поэтому я пытаюсь понять всю концепцию отсюда.

15 ответов

Решение

Просто пройдите приведенный ниже код.

SmtpClient smtpClient = new SmtpClient("mail.MyWebsiteDomainName.com", 25);

smtpClient.Credentials = new System.Net.NetworkCredential("info@MyWebsiteDomainName.com", "myIDPassword");
smtpClient.UseDefaultCredentials = true;
smtpClient.DeliveryMethod = SmtpDeliveryMethod.Network;
smtpClient.EnableSsl = true;
MailMessage mail = new MailMessage();

//Setting From , To and CC
mail.From = new MailAddress("info@MyWebsiteDomainName", "MyWeb Site");
mail.To.Add(new MailAddress("info@MyWebsiteDomainName"));
mail.CC.Add(new MailAddress("MyEmailID@gmail.com"));

smtpClient.Send(mail);

Попробуйте использовать этот код вместо этого. Примечание. В поле "От адреса" укажите свой правильный адрес электронной почты и пароль.

protected void btn_send_Click(object sender, EventArgs e)
{

    System.Net.Mail.MailMessage mail = new System.Net.Mail.MailMessage();
    mail.To.Add("to gmail address");
    mail.From = new MailAddress("from gmail address", "Email head", System.Text.Encoding.UTF8);
    mail.Subject = "This mail is send from asp.net application";
    mail.SubjectEncoding = System.Text.Encoding.UTF8;
    mail.Body = "This is Email Body Text";
    mail.BodyEncoding = System.Text.Encoding.UTF8;
    mail.IsBodyHtml = true;
    mail.Priority = MailPriority.High;
    SmtpClient client = new SmtpClient();
    client.Credentials = new System.Net.NetworkCredential("from gmail address", "your gmail account password");
    client.Port = 587;
    client.Host = "smtp.gmail.com";
    client.EnableSsl = true;
    try
    {
        client.Send(mail);
        Page.RegisterStartupScript("UserMsg", "<script>alert('Successfully Send...');if(alert){ window.location='SendMail.aspx';}</script>");
    }
    catch (Exception ex)
    {
        Exception ex2 = ex;
        string errorMessage = string.Empty;
        while (ex2 != null)
        {
            errorMessage += ex2.ToString();
            ex2 = ex2.InnerException;
        }
        Page.RegisterStartupScript("UserMsg", "<script>alert('Sending Failed...');if(alert){ window.location='SendMail.aspx';}</script>");
    }
}

Вы можете попробовать это, используя Hotmail, как это:-

MailMessage o = new MailMessage("From", "To","Subject", "Body");
NetworkCredential netCred= new NetworkCredential("Sender Email","Sender Password");
SmtpClient smtpobj= new SmtpClient("smtp.live.com", 587); 
smtpobj.EnableSsl = true;
smtpobj.Credentials = netCred;
smtpobj.Send(o);

Попробуйте следующее:

try
{
    var fromEmailAddress =  ConfigurationManager.AppSettings["FromEmailAddress"].ToString();
    var fromEmailDisplayName = ConfigurationManager.AppSettings["FromEmailDisplayName"].ToString();
    var fromEmailPassword = ConfigurationManager.AppSettings["FromEmailPassword"].ToString();
    var smtpHost = ConfigurationManager.AppSettings["SMTPHost"].ToString();
    var smtpPort = ConfigurationManager.AppSettings["SMTPPort"].ToString();

    string body = "Your registration has been done successfully. Thank you.";
    MailMessage message = new MailMessage(new MailAddress(fromEmailAddress, fromEmailDisplayName), new MailAddress(ud.LoginId, ud.FullName));
    message.Subject = "Thank You For Your Registration";
    message.IsBodyHtml = true;
    message.Body = body;

    var client = new SmtpClient();
    client.Credentials = new NetworkCredential(fromEmailAddress, fromEmailPassword);
    client.Host = smtpHost;
    client.EnableSsl = true;
    client.Port = !string.IsNullOrEmpty(smtpPort) ? Convert.ToInt32(smtpPort) : 0;
    client.Send(message);
}
catch (Exception ex)
{
    throw (new Exception("Mail send failed to loginId " + ud.LoginId + ", though registration done."));
}

А затем в вашем web.config добавить следующее между

<!--Email Config-->
<add key="FromEmailAddress" value="sender emailaddress"/>
<add key="FromEmailDisplayName" value="Display Name"/>
<add key="FromEmailPassword" value="sender Password"/>
<add key="SMTPHost" value="smtp-proxy.tm.net.my"/>
<add key="SMTPPort" value="smptp Port"/>

Вы можете попробовать MailKit

                MimeMessage mailMessage = new MimeMessage();
                mailMessage.From.Add(new MailboxAddress(senderName, sender@address.com));
                mailMessage.Sender = new MailboxAddress(senderName, sender@address.com);
                mailMessage.To.Add(new MailboxAddress(emailid, emailid));
                mailMessage.Subject = subject;
                mailMessage.ReplyTo.Add(new MailboxAddress(replyToAddress));
                mailMessage.Subject = subject;
                var builder = new BodyBuilder();
                builder.TextBody = "Hello There";           
                try
                {
                    using (var smtpClient = new SmtpClient())
                    {
                        smtpClient.Connect("HostName", "Port", MailKit.Security.SecureSocketOptions.None);
                        smtpClient.Authenticate("user@name.com", "password");

                        smtpClient.Send(mailMessage);
                        Console.WriteLine("Success");
                    }
                }
                catch (SmtpCommandException ex)
                {
                    Console.WriteLine(ex.ToString());              
                }
                catch (Exception ex)
                {
                    Console.WriteLine(ex.ToString());                
                }
For more information you can [download package][1]


  [1]: https://www.nuget.org/packages/MailKit

Просто передайте такой параметр, как body - контент (запрос) из
темы клиента - тема, определенная в
имени пользователя темы письма - ничего не назовите ничего
mail - mail (обязательно)

         public static bool SendMail(String body, String subject, string username, String mail)
    {
        bool isSendSuccess = false;
        try
        {
            var fromEmailAddress = ConfigurationManager.AppSettings["FromEmailAddress"].ToString();
            var fromEmailDisplayName = ConfigurationManager.AppSettings["FromEmailDisplayName"].ToString();
            var fromEmailPassword = ConfigurationManager.AppSettings["FromEmailPassword"].ToString();
            var smtpHost = ConfigurationManager.AppSettings["SMTPHost"].ToString();
            var smtpPort = ConfigurationManager.AppSettings["SMTPPort"].ToString();


            MailMessage message = new MailMessage(new MailAddress(fromEmailAddress, fromEmailDisplayName),
                new MailAddress(mail, username));
            message.Subject = subject;
            message.IsBodyHtml = true;
            message.Body = body;

            var client = new SmtpClient();
            client.UseDefaultCredentials = false;
            client.Credentials = new NetworkCredential(fromEmailAddress, fromEmailPassword);
            client.Host = smtpHost;
            client.EnableSsl = false;
            client.Port = !string.IsNullOrEmpty(smtpPort) ? Convert.ToInt32(smtpPort) : 0;
            client.Send(message);
            isSendSuccess = true;
        }
        catch (Exception ex)
        {
            throw (new Exception("Mail send failed to loginId " + mail + ", though registration done."+ex.ToString()+"\n"+ex.StackTrace));
        }

        return isSendSuccess;
    }

если вы используете go daddy server, эта работа. добавьте это в web.config

        <appSettings>
    ---other ---setting

    <add key="FromEmailAddress" value="myemail@gmail.com" />
    <add key="FromEmailDisplayName" value="anyname" />
    <add key="FromEmailPassword" value="mypassword@" />
    <add key="SMTPHost" value="relay-hosting.secureserver.net" />
    <add key="SMTPPort" value="25" />

</appSettings>

если вы используете localhost или vps server, измените эту конфигурацию на эту

       <appSettings>
    ---other ---setting

    <add key="FromEmailAddress" value="myemail@gmail.com" />
    <add key="FromEmailDisplayName" value="anyname" />
    <add key="FromEmailPassword" value="mypassword@" />
    <add key="SMTPHost" value="smtp.gmail.com" /> 
    <add key="SMTPPort" value="587" />
</appSettings>

изменить код

                client.EnableSsl = true;

если вы используете Gmail, включите безопасное приложение. используя эту ссылку https://myaccount.google.com/lesssecureapps?pli=1&amp;rapt=AEjHL4Pd6h3XxE663Flvd-FfeRXxW_eNrIsGTBlZklgkAHZEeuHvheCQuZ1-djB9uIKaDU0-22

          using System;
    using System.Collections.Generic;
    using System.Linq;
    using System.Web;
    using System.Globalization;
    using System.Text.RegularExpressions;
    
    /// <summary>
    /// Summary description for RegexUtilities
    /// </summary>
    public class RegexUtilities
    {
        bool InValid = false;
    
        public bool IsValidEmail(string strIn)
        {
            InValid = false;
            if (String.IsNullOrEmpty(strIn))
                return false;
    
            // Use IdnMapping class to convert Unicode domain names.
            strIn = Regex.Replace(strIn, @"(@)(.+)$", this.DomainMapper);
            if (InValid)
                return false;
    
            // Return true if strIn is in valid e-mail format. 
            return Regex.IsMatch(strIn, @"^(?("")(""[^""]+?""@)|(([0-9a-z]((\.(?!\.))|[-!#\$%&'\*\+/=\?\^`\{\}\|~\w])*)(?<=[0-9a-z])@))" + @"(?(\[)(\[(\d{1,3}\.){3}\d{1,3}\])|(([0-9a-z][-\w]*[0-9a-z]*\.)+[a-z0-9]{2,17}))$",
                   RegexOptions.IgnoreCase);
        }
    
        private string DomainMapper(Match match)
        {
            // IdnMapping class with default property values.
            IdnMapping idn = new IdnMapping();
    
            string domainName = match.Groups[2].Value;
            try
            {
                domainName = idn.GetAscii(domainName);
            }
            catch (ArgumentException)
            {
                InValid = true;
            }
            return match.Groups[1].Value + domainName;
        }
    
    }



 private void GetSendEmInfo()
    {
        #region For Get All Type Email Informations..!!
        IPL.DoId = ddlName.SelectedValue;
        DataTable dt = IdBL.GetEmailS(IPL);
        if (dt.Rows.Count > 0)
        {
            hid_MailId.Value = dt.Rows[0]["MailId"].ToString();
            hid_UsedPName.Value = dt.Rows[0]["UName"].ToString();
            hid_EmailSubject.Value = dt.Rows[0]["EmailSubject"].ToString();
            hid_EmailBody.Value = dt.Rows[0]["EmailBody"].ToString();
            hid_EmailIdName.Value = dt.Rows[0]["EmailIdName"].ToString();
            hid_EmPass.Value = dt.Rows[0]["EPass"].ToString();
            hid_SeName.Value = dt.Rows[0]["SenName"].ToString();
            hid_TNo.Value = dt.Rows[0]["TeNo"].ToString();
            hid_EmaLimit.Value = dt.Rows[0]["EmailLimit"].ToString();
            hidlink.Value = dt.Rows[0][link"].ToString();
        }
        #endregion

        #region For Set Some Local Variables..!!
        int StartLmt, FinalLmt, SendCurrentMail;
        StartLmt = FinalLmt = SendCurrentMail = 0;
        bool Valid_LimitMail;
        Valid_LimitMail = true;
        /**For Get Finalize Limit For Send Mail**/
        FinalLmt = Convert.ToInt32(hid_EmailmaxLimit.Value);
        #region For Check Email Valid Limits..!!
        if (FinalLmt > 0)
        {
            Valid_LimitMail = true;
        }
        else
        {
            Valid_LimitMail = false;
        }
        #endregion
        /**For Get Finalize Limit For Send Mail**/
        #endregion

        if (Valid_LimitMail == true)
        {
            #region For Send Current Email Status..!!
            bool EmaiValid;
            string CreateFileName;
            string retmailflg = null;
            EmaiValid = false;
            #endregion

            #region For Set Start Limit And FinalLimit Send No Of Email..!!
            mPL.SendDate = DateTime.Now.ToString("dd-MMM-yyyy");
            DataTable dtsendEmail = m1BL.GetEmailSendLog(mPL);
            if (dtsendEmail.Rows.Count > 0)
            {
                StartLmt = Convert.ToInt32(dtsendEmail.Rows[0]["SendNo_Of_Email"].ToString());
            }
            else
            {
                StartLmt = 0;
            }
            #endregion

            #region For Find Grid View Controls..!!
            for (int i = 0; i < GrdEm.Rows.Count; i++)
            {
                #region For Find Grid view Controls..!!
                CheckBox Chk_SelectOne = (CheckBox)GrdEmp.Rows[i].FindControl("chkSingle");
                Label lbl_No = (Label)GrdEmAtt.Rows[i].FindControl("lblGrdCode");
                lblCode.Value = lbl_InNo.Text;

                Label lbl_EmailId = (Label)GrdEomAtt.Rows[i].FindControl("lblGrdEmpEmail");

                #endregion

                /**Region For If Check Box Checked Then**/
                if (Chk_SelectOne.Checked == true)
                {
                    if (!string.IsNullOrEmpty(lbl_EmailId.Text))
                    {
                        #region For When Check Box Checked..!!
                        /**If Start Limit Less Or Equal To Then Condition Performs**/
                        if (StartLmt < FinalLmt)
                        {
                            StartLmt = StartLmt + 1;
                        }
                        else
                        {
                            Valid_LimitMail = false;
                            EmaiValid = false;
                        }
                        /**End Region**/
                        string[] SplitClients_Email = lbl_EmailId.Text.Split(',');
                        string Send_Email, Hold_Email;
                        Send_Email = Hold_Email = "";

                        int CountEmail;/**Region For Count Total Email**/
                        CountEmail = 0;/**First Time Email Counts Zero**/

                        Hold_Email = SplitClients_Email[0].ToString().Trim().TrimEnd().TrimStart().ToString();
                        /**Region For If Clients Have One Email**/
                        #region For First Emails Send On Client..!!
                        if (SplitClients_Email[0].ToString() != "")
                        {
                            if (EmailRegex.IsValidEmail(Hold_Email))
                            {
                                Send_Email = Hold_Email;
                                CountEmail = 1;
                                EmaiValid = true;
                            }
                            else
                            {
                                EmaiValid = false;
                            }
                        }
                        #endregion
                        /**Region For If Clients Have One Email**/
                        /**Region For If Clients Have Two Email**/

                        /**Region For If Clients Have Two Email**/
                        if (EmaiValid == true)
                        {
                            #region For Create Email Body And Create File Name..!!
                            //fofile = Server.MapPath("PDFs");
                            fofile = Server.MapPath("~/vvv/vvvv/") + "/";
                            CreateFileName = lbl_INo.Text.ToString() + "_1" + ".Pdf";/**Create File Name**/
                            string[] orimail = Send_Email.Split(',');
                            string Billbody, TempInvoiceId;
                            // DateTime dtLstdate = new DateTime(Convert.ToInt32(txtYear.Text), Convert.ToInt32(ddlMonth.SelectedValue), 16);

                            //  DateTime IndtLmt = dtLstdate.AddMonths(1);
                            TempInvoiceId = "";

                            //byte[] Buffer = Encrypt.Encryptiondata(lbl_InvoiceNo.Text.ToString());
                            //TempInvoiceId = Convert.ToBase64String(Buffer);


                            #region Create Encrypted Path


                            byte[] EncCode = Encrypt.Encryptiondata(lbl_INo.Text);
                            hidEncrypteCode.Value = Convert.ToBase64String(EncECode);
                            #endregion

                        

                            //#region Create Email Body !!
                            //body = hid_EmailBody.Value.Replace("@greeting", lbl_CoName.Text).Replace("@free", hid_ToNo.Value).Replace("@llnk", "<a style='font-family: Tahoma; font-size: 10pt; color: #800000; font-weight: bold' href='http://1ccccc/ccc/ccc/ccc.aspx?EC=" + hidEncryptedCode.Value+ "' > C cccccccc </a>");
                          

                            body = hid_EmailBody.Value.Replace("@greeting", "Hii").Replace("@No", hid_No.Value);/*For Mail*/
                            //#endregion



                            #region For Email Sender Informations..!!
                            for (int j = 0; j < CountEmail; j++)
                            {
                                //if (File.Exists(fofile + "\\" + CreateFileName))
                                //{
                                #region
                                lbl_EmailId.Text = orimail[j];
                                retmailflg = "";

                                /**Region For Send Email For Clients**/
                                //retmailflg = SendPreMail("Wp From " + lbl_CName.Text + "", body, lbl_EmailId.Text, lbl_IeNo.Text, hid_EmailIdName.Value, hid_EmailPassword.Value);
                                retmailflg = SendPreMail(hid_EmailSubject.Value, Body, lbl_EmailId.Text, lbl_No.Text, hid_EmailIdName.Value, hid_EmailPassword.Value);
                                /**End Region**/

                                /**Region For Create Send Email Log  When Email Send Successfully**/
                                if (retmailflg == "True")
                                {
                                    SendCurrentMail = Convert.ToInt32(SendCurrentMail) + 1;
                                    StartLmt = Convert.ToInt32(StartLmt) + 1;

                                    if (SendCurrentMail > 0)
                                    {
                                        CreateEmailLog(lbl_InNo.Text, StartLmt, hid_EmailIdName.Value, lbl_EmailId.Text);
                                        
                                    }
                                }
                                

                                /**End Region**/
                                #endregion
                                //}
                            }
                            #endregion
                        }
                        #endregion
                    }
                }
                /**End Region**/
            }
            #endregion

        }
       
    }
    private void CreateEmailLog(string UniqueId, int StartLmt, string FromEmailId, string TotxtEmailId)
    {
        FPL.EmailId_From = FromEmailId;
        FPL.To_EmailId = TotxtEmailId;
        FPL.SendDate = DateTime.Now.ToString("dd-MMM-yyyy");
        FPL.EmailUniqueId = UniqueId;
        FPL.SendNo_Of_Email = StartLmt.ToString();
        FPL.LoginUserId = Session["LoginUserId"].ToString();
        int i = FBL.InsertEmaDoc(FPL);
    }

    public string SendPreMail(string emsub, string embody, string EmailId, string FileId, string EmailFromId, string Password)
    {
        string retval = "False";
        try
        {
            string emailBody, emailSubject, emailToList, emailFrom,
            accountPassword, smtpServer;
            bool enableSSL;
            int port;

            emailBody = embody;
            emailSubject = emsub;
            emailToList = EmailId;
            emailFrom = EmailFromId;
            accountPassword = Password;
            smtpServer = "smtp.gmail.com";
            enableSSL = true;
            port = 587;

            string crefilename;
            string fofile;
            fofile = Server.MapPath("PDF");
            crefilename = FileId + ".Pdf";

            string[] att = { crefilename };

            string retemail, insertqry;
            retemail = "";

            retemail = SendEmail(emailBody, emailSubject, emailFrom, emailToList, att, smtpServer, enableSSL, accountPassword, port);

            if (retemail == "True")
            {

                retval = retemail;
            }
        }
        catch
        {
            retval = "False";
        }
        finally
        {

        }
        return retval;
    }

    public string SendEmail(string emailBody, string emailSubject, string emailFrom, string emailToList, string[] attachedFiles, string smtpIPAddress, bool enableSSL, string accountPassword, int port)
    {
        MailMessage mail = new MailMessage();
        string retflg;
        retflg = "False";
        try
        {
            mail.From = new MailAddress(emailFrom);
            if (emailToList.Contains(";"))
            {
                emailToList = emailToList.Replace(";", ",");
            }
            mail.To.Add(emailToList);

            mail.Subject = emailSubject;
            mail.IsBodyHtml = true;
            mail.Body = emailBody;


            SmtpClient smtp = new SmtpClient();
            smtp.Host = "smtp.gmail.com";
            smtp.EnableSsl = true;
            NetworkCredential NetworkCred = new NetworkCredential(emailFrom, accountPassword);
            smtp.UseDefaultCredentials = true;
            smtp.Credentials = NetworkCred;
            smtp.Port = 587;
            smtp.Send(mail);
            retflg = "True";

        }
        catch
        {
            retflg = "False";
        }
        finally
        {
            mail.Dispose();
        }
        return retflg;
    }

Проверьте это.... это работает

http://www.aspnettutorials.com/tutorials/email/email-aspnet2-csharp/

using System;
using System.Data;
using System.Configuration;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
using System.Net.Mail;

public partial class _Default : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {

    }

    protected void btnSubmit_Click(object sender, EventArgs e)
    {
        try
        {
            MailMessage message = new MailMessage(txtFrom.Text, txtTo.Text, txtSubject.Text, txtBody.Text);
            SmtpClient emailClient = new SmtpClient(txtSMTPServer.Text);
            emailClient.Send(message);
            litStatus.Text = "Message Sent";
        }
        catch (Exception ex)
        {
            litStatus.Text=ex.ToString();
        }
    }
}

Если вы хотите создать ваши электронные письма в бритве, вы можете использовать Mailzory. Также вы можете скачать пакет nuget здесь.

// template path
var viewPath = Path.Combine("Views/Emails", "hello.cshtml");
// read the content of template and pass it to the Email constructor
var template = File.ReadAllText(viewPath);

var email = new Email(template);

// set ViewBag properties
email.ViewBag.Name = "Johnny";
email.ViewBag.Content = "Mailzory Is Funny";

// send email
var task = email.SendAsync("mailzory@outlook.com", "subject");
task.Wait()

Это просто отлично работает для меня.

    public  void sendEmail(string body)
    {
        if (String.IsNullOrEmpty(email))
            return;
        try
        {
            MailMessage mail = new MailMessage();
            mail.To.Add(email);
            mail.To.Add("test@gmail.com");
            mail.From = new MailAddress("abc@gmail.com");
            mail.Subject = "sub";

            mail.Body = body;

            mail.IsBodyHtml = true;
            SmtpClient smtp = new SmtpClient();
            smtp.Host = "smtp.gmail.com"; //Or Your SMTP Server Address
            smtp.Credentials = new System.Net.NetworkCredential
                 ("yourgmail@gmail.com", "Yourpassword"); // ***use valid credentials***
            smtp.Port = 587;

            //Or your Smtp Email ID and Password
            smtp.EnableSsl = true;
            smtp.Send(mail);
        }
        catch (Exception ex)
        {
            print("Exception in sendEmail:" + ex.Message);
        }
    }

Google может блокировать попытки входа из некоторых приложений или устройств, которые не используют современные стандарты безопасности. Поскольку эти приложения и устройства легче взломать, их блокировка помогает защитить вашу учетную запись.

Вот некоторые примеры приложений, не поддерживающих новейшие стандарты безопасности:

  1. Приложение "Почта" на вашем iPhone или iPad с iOS 6 или более ранней версии.
  2. Приложение Почта на вашем телефоне с Windows до версии 8.1
  3. Некоторые почтовые клиенты для настольных ПК, такие как Microsoft Outlook и Mozilla Thunderbird

Следовательно, вы должны включить менее безопасный вход (или менее безопасный доступ к приложениям ) в своей учетной записи Google.

После входа в учетную запись Google перейдите по ссылке:

https://www.google.com/settings/security/lesssecureapps или https://myaccount.google.com/lesssecureapps

В C # вы можете использовать следующий код:

        public static bool SendEmail()
  {
        try
        {
            using (MailMessage mail = new MailMessage())
            {
                mail.From = new MailAddress("sender email");
                mail.To.Add("receiver email");
                mail.Subject = "Hello World";
                mail.Body = "Hello";
                mail.IsBodyHtml = true;

                using (SmtpClient smtp = new SmtpClient("smtp.gmail.com", 587))
                {
                    smtp.Credentials = new NetworkCredential("sender email", "password");
                    smtp.EnableSsl = true;
                    smtp.Send(mail);
                    return true;
                }
            }
        }
        catch
        {
            return false;
        }
   }

Этот код не работает в Outlook , Hotmail

Согласно этому:

SmtpClient и его сеть типов плохо спроектированы, мы настоятельно рекомендуем вам использовать вместо них https://github.com/jstedfast/MailKit и https://github.com/jstedfast/MimeKit.

Ссылка: https://docs.microsoft.com/en-us/dotnet/api/system.net.mail.smtpclient?view=netframework-4.8

Лучше использовать MailKit для отправки писем:

var message = new MimeMessage ();
            message.From.Add (new MailboxAddress ("Joey Tribbiani", "joey@friends.com"));
            message.To.Add (new MailboxAddress ("Mrs. Chanandler Bong", "chandler@friends.com"));
            message.Subject = "How you doin'?";

            message.Body = new TextPart ("plain") {
                Text = @"Hey Chandler,
I just wanted to let you know that Monica and I were going to go play some paintball, you in?
-- Joey"
            };

            using (var client = new SmtpClient ()) {
                // For demo-purposes, accept all SSL certificates (in case the server supports STARTTLS)
                client.ServerCertificateValidationCallback = (s,c,h,e) => true;

                client.Connect ("smtp.friends.com", 587, false);

                // Note: only needed if the SMTP server requires authentication
                client.Authenticate ("joey", "password");

                client.Send (message);
                client.Disconnect (true);
            }

Обновление ответа 2023 г.

Код C# для службы электронной почты (GMAIL)

      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();
            }

        }
    }
}

Для получения дополнительной помощи вы можете обратиться по адресу: https://www.techaeblogs.live/2022/06/how-to-send-email-using-gmail.html .

Это самый простой скрипт для тестирования.

<%@ Import Namespace="System.Net" %> 
<%@ Import Namespace="System.Net.Mail" %> 

<script language="C#" runat="server"> 
    protected void Page_Load(object sender, EventArgs e) 
    { 
       //create the mail message 
        MailMessage mail = new MailMessage(); 

        //set the addresses 
        mail.From = new MailAddress("From email account"); 
        mail.To.Add("To email account"); 

        //set the content 
        mail.Subject = "This is a test email from C# script"; 
        mail.Body = "This is a test email from C# script"; 
        //send the message 
         SmtpClient smtp = new SmtpClient("mail.domainname.com"); 

         NetworkCredential Credentials = new NetworkCredential("to email account", "Password"); 
         smtp.Credentials = Credentials;
         smtp.Send(mail); 
         lblMessage.Text = "Mail Sent"; 
    } 
</script> 
<html> 
<body> 
    <form runat="server"> 
        <asp:Label id="lblMessage" runat="server"></asp:Label> 
    </form> 
</body>
MailMessage mm = new MailMessage(txtEmail.Text, txtTo.Text);
mm.Subject = txtSubject.Text;
mm.Body = txtBody.Text;
if (fuAttachment.HasFile)//file upload select or not
{
    string FileName = Path.GetFileName(fuAttachment.PostedFile.FileName);
    mm.Attachments.Add(new Attachment(fuAttachment.PostedFile.InputStream, FileName));
}
mm.IsBodyHtml = false;
SmtpClient smtp = new SmtpClient();
smtp.Host = "smtp.gmail.com";
smtp.EnableSsl = true;
NetworkCredential NetworkCred = new NetworkCredential(txtEmail.Text, txtPassword.Text);
smtp.UseDefaultCredentials = true;
smtp.Credentials = NetworkCred;
smtp.Port = 587;
smtp.Send(mm);
Response.write("Send Mail");

Просмотр видео: https://www.youtube.com/watch?v=bUUNv-19QAI

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