sendmail - How to get Dynamic Data in email newsletter from the website in asp.net c#? -

i have newsletter design in have bind data dynamically , send mail users in asp.net c# through noreply@xyz.com tried getting error of authentication if knows please sort out problem.

 mailmessage msg = new mailmessage();         mailaddress frommail = new mailaddress("abc@gmail.com");         // sender e-mail address.         msg.from = frommail;         // recipient e-mail address.         msg.to.add(new mailaddress("xyz@gmail.com"));         // subject of e-mail         msg.subject = "send gridivew in email";         msg.body += "please check below data <br/><br/>";         msg.body += getgridviewdata(gvuserinfo);         msg.isbodyhtml = true;         string ssmtpserver = "";         ssmtpserver = "smtp.gmail.com";         smtpclient = new smtpclient();         a.host = ssmtpserver;         a.enablessl = true;         a.port = 587;         a.deliverymethod = system.net.mail.smtpdeliverymethod.network;         a.credentials = new networkcredential("abc@gmail.com", "abc@123");         a.send(msg); 

grid view code

 public string getgridviewdata(gridview gv) {     stringbuilder strbuilder = new stringbuilder();     stringwriter strwriter = new stringwriter(strbuilder);     htmltextwriter htw = new htmltextwriter(strwriter);     gv.rendercontrol(htw);     return strbuilder.tostring(); }