Sometimes google blocks the third party access, so you have to enable Less-Secure Sign In

Hi Uttam

  I tried but still same problem, Below is my code

Email.BodyEncoding = Encoding.UTF8;
                                Email.IsBodyHtml = true;
                                Email.Priority = MailPriority.Normal;
                                SmtpClient sc = new SmtpClient("smtp.gmail.com", 587);
                                sc.Credentials = new System.Net.NetworkCredential("[email protected]", "test123@");

                                sc.EnableSsl = true;
                                sc.UseDefaultCredentials = false;
                                sc.Send(Email);

Thanks

Google may block sign-in attempts from some apps or devices that do not use modern security standards. Since these apps and devices are easier to break into, blocking them helps keep your account safer.

Therefore, you have to enable Less Secure Sign-In (or Less secure app access) in your google account.

After signing into your Google account, go to:

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

In C#, you can use the following code:

using (MailMessage mail = new MailMessage())
{
    mail.From = new MailAddress("[email protected]");
    mail.To.Add("[email protected]");
    mail.Subject = "Hello World";
    mail.Body = "
Hello
";
    mail.IsBodyHtml = true;
    mail.Attachments.Add(new Attachment("C:\\file.zip"));

    using (SmtpClient smtp = new SmtpClient("smtp.gmail.com", 587))
    {
        smtp.Credentials = new NetworkCredential("[email protected]", "password");
        smtp.EnableSsl = true;
        smtp.Send(mail);
    }
}

Hi Ramco,

Please refer below link, hope this might help you.

https://www.aspsnippets.com/Articles/Send-email-using-Gmail-SMTP-Mail-Server-in-ASPNet.aspx

https://www.aspsnippets.com/Articles/GMAIL-Error-The-SMTP-server-requires-a-secure-connection-or-the-client-was-not-authenticated.aspx

Hi Vishal

  Below is the code but still same problem , Even in Gmail i have set Less secure App Access = "On".

Email.Body = BodyStr;

                                Email.BodyEncoding = Encoding.UTF8;
                                Email.IsBodyHtml = true;
                                Email.Priority = MailPriority.Normal;
                                SmtpClient sc = new SmtpClient("smtp.gmail.com", 587);
                                sc.Credentials = new System.Net.NetworkCredential("[email protected]", "test123@");

                                sc.EnableSsl = true;
                                sc.UseDefaultCredentials = false;
                                sc.Send(Email);

Thanks

Try this, hope this will work

sc.Credentials = new System.Net.NetworkCredential("[email protected]", "password");
sc.EnableSsl = true;
sc.UseDefaultCredentials = false;

Hi

  Even then same error

Thanks

Hi Ramco,

try this by setting this

ss.UseDefaultCredentials = true;