Sending email problem by Gmail account

I'm trying to send a email in C# using Gmail. I want the 'from' header to have another my own specified email address whenever user receive email. Could anyone please tell me how can I do this?

MailMessage mailMsg = new MailMessage();
SmtpClient client = new SmtpClient();

client.Port = 587;
client.Host = "smtp.gmail.com";
client.EnableSsl = true;
client.Credentials = new System.Net.NetworkCredential(username, passwor开发者_如何转开发d);
MailAddress mailAdd = new MailAddress("jack2@gmail.com");

mailMsg.Sender = new MailAddress(username);
mailMsg.From = mailAdd;
//mailMsg.Headers.Add("Sender",username);
mailMsg.Bcc.Add(builder.ToString());

mailMsg.Subject = txtSubject.Text;
mailMsg.Body = txtBody.Text;
mailMsg.IsBodyHtml = chkHtmlBody.Checked;
if (System.IO.File.Exists(txtAttechments.Text))
{
System.Net.Mail.Attachment attechment = new Attachment(txtAttechments.Text);
mailMsg.Attachments.Add(attechment);
}

client.Send(mailMsg);

In above code 'username' and 'password' fields contain another email address and password. The received email having 'from' header with value

TRY this if your mail provide is not gmail and also not using IMAP services.

MailMessage mailMsg = new MailMessage();
SmtpClient client = new SmtpClient();

client.Port = 587;
client.Host = "mail.youdomain.com"; //////EDITED
client.EnableSsl = false; //////EDITED
client.Credentials = new System.Net.NetworkCredential(username, password);
MailAddress mailAdd = new MailAddress("jack2@gmail.com");

mailMsg.Sender = new MailAddress(username);
mailMsg.From = mailAdd;
//mailMsg.Headers.Add("Sender",username);
mailMsg.Bcc.Add(builder.ToString());

mailMsg.Subject = txtSubject.Text;
mailMsg.Body = txtBody.Text;
mailMsg.IsBodyHtml = chkHtmlBody.Checked;
if (System.IO.File.Exists(txtAttechments.Text))
{
System.Net.Mail.Attachment attechment = new Attachment(txtAttechments.Text);
mailMsg.Attachments.Add(attechment);
}

client.Send(mailMsg);