email from someaddress@company.com in asp.net using gmail SMTP authentication
msg.From = new MailAddress(gMailAccount);

NetworkCredential loginInfo = new NetworkCredential(gMailAccount, password)

<mailSettings>
  <smtp from="someone@companyname.com">
    <network enableSsl="false" host="smtp.gmail.com"
             password="secretone" port="25" userName="user@gmail.com" />
  </smtp>
</mailSettings>

var smtp = new SmtpClient();
smtp.Send(new MailMessage("someone@companyname.com", "to@domain.com")
{
    IsBodyHtml = true,
    Subject = "Some subject",
    Body = "add html code here"
});