Send Email Using Gmail in ASP.NET

If you want to send email using your Gmail account or using Gmail's smtp server in ASP.NET application or if you don't have a working smtp server to send mails using your ASP.NET application or aspx page than sending e-mail using Gmail is best option.

you need to write code like this

using System.Net.Mail;

Now write this code in click event of button

C# code

protected void Button1_Click(object sender, EventArgs e)
{
  MailMessage mail = new MailMessage();
  mail.To.Add("jainamit.agra@gmail.com");
  mail.To.Add("amit_jain_online@yahoo.com");
  mail.From = new MailAddress("jainamit.agra@gmail.com");
  mail.Subject = "Email using Gmail";

  string Body = "Hi, this mail is to test sending mail"+ 
                "using Gmail in ASP.NET";
  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
       ("YourUserName@gmail.com","YourGmailPassword");
//Or your Smtp Email ID and Password
  smtp.EnableSsl = true;
  smtp.Send(mail);
}

VB.NET code

Imports System.Net.Mail
 
Protected  Sub Button1_Click
(ByVal sender As Object, ByVal e As EventArgs)
  Dim mail As MailMessage =  New MailMessage() 
  mail.To.Add("jainamit.agra@gmail.com")
  mail.To.Add("amit_jain_online@yahoo.com")
  mail.From = New MailAddress("jainamit.agra@gmail.com")
  mail.Subject = "Email using Gmail"
 
  String Body = "Hi, this mail is to test sending mail"+ 
                "using Gmail in ASP.NET"
  mail.Body = Body
 
  mail.IsBodyHtml = True
  Dim smtp As SmtpClient =  New SmtpClient() 
  smtp.Host = "smtp.gmail.com" //Or Your SMTP Server Address
  smtp.Credentials = New System.Net.NetworkCredential
       ("YourUserName@gmail.com","YourGmailPassword")
  smtp.EnableSsl = True
  smtp.Send(mail)
End Sub

You also need to enable POP by going to settings > Forwarding and POP in your gmail account

Change YourUserName@gmail.com to your gmail ID and YourGmailPassword to Your password for Gmail account and test the code.

If your are getting error mentioned below
"The SMTP server requires a secure connection or the client was not authenticated. The server response was: 5.5.1 Authentication Required."

than you need to check your Gmail username and password.

If you are behind proxy Server then you need to write below mentioned code in your web.config file

<system.net>
<defaultProxy>
<proxy proxyaddress="YourProxyIpAddress"/>
defaultProxy>
system.net>

If you are still having problems them try changing port number to 587

smtp.Host = "smtp.gmail.com,587";

If you still having problems then try changing code as mentioned below

SmtpClient smtp = new SmtpClient();
smtp.Host = "smtp.gmail.com";
smtp.Port = 587;
smtp.UseDefaultCredentials = False;
smtp.Credentials = new System.Net.NetworkCredential
("YourUserName@gmail.com","YourGmailPassword");
smtp.EnableSsl = true;
smtp.Send(mail);

Hope this helps