Hi,
Due to error below, what reason can be identified further?

Problem encountered to send out Email notification to user. 535 Authentication failed. Restarting authentication process. at EASendMail.SmtpClient.(String , String ) at EASendMail.SmtpClient.(SmtpServer , Boolean , String ) at EASendMail.SmtpClient.(SmtpServer , Boolean , String& ) at EASendMail.SmtpClient.Connect(SmtpServer server) at EASendMail.SmtpClient.SendMail(SmtpServer server, SmtpMail mail) at Login._Default.Page_Load(Object sender, EventArgs e)

with codes like

oMail.From = "sender@???.com";
//oMail.From = "xxx";
//oMail.To = tb_email.Text;
oMail.To = "???n@gmail.com";
//oMail.To = "xxyy";
oMail.Subject = "Test";

oMail.HtmlBody = "???";
//SmtpServer oServer = new SmtpServer("localhost");
SmtpServer oServer = new SmtpServer("www.???.com");
//oServer.User = "sender";
oServer.User = "sender@???.com";
oServer.Password = "???";
oServer.ConnectType = SmtpConnectType.ConnectSSLAuto;

try
{
oSmtp.LogFileName = "c:/dp2/smtp.txt";
oSmtp.SendMail(oServer, oMail);

535 Authentication failed. Restarting authentication process is returned by your server.

It means your user/password is not accepted by your server, are you sure the user/password is correct? I thought you should contact server administrator for assistance.

Hi,
The user account and password are fine.

What could be any other reasons?

This error was returned by your server:

535 Authentication failed. Restarting authentication process

You have to ask server administrator for assistance. If your server administrator disabled your SMTP authentication, you will get the error even with correct user/password.