The Smpt command order is incorrect. Server Response: Error: need EHLO and AUTH first !, Smptehlo

The Smpt command order is incorrect. Server Response: Error: need EHLO and AUTH first !, Smptehlo

I just found that I couldn't use emails sent from my previous QQ mailbox. I found the following reason: I was not added (EnableSsl SSL encrypted connection), and I suddenly felt very bad, in the past, QQ mail had no such restriction. It may have been recently added.

Well, let's just start from scratch and take care of the newcomers O ~

1. First enable "POP3/SMTP Service" in the QQ mailbox"

2. Obtain the "authorization code"

After you activate the service in the previous step, you will be prompted with an "authorization code". If you have activated the service, you can check it.

3. Encoding

SmtpClient smtpClient = new SmtpClient ();

SmtpClient. EnableSsl = true;

SmtpClient. usedefadefacredentials = false;

SmtpClient. DeliveryMethod = SmtpDeliveryMethod. Network; // specify the email sending Method

SmtpClient. Host = smtpServer; // specify the SMTP server

SmtpClient. Credentials = new System. Net. NetworkCredential (userFrom, userPassword); // user name and authorization code

// Send email settings

MailMessage mailMessage = new MailMessage (userFrom, MailTo); // sender and recipient

MailMessage. Subject = mailSubject; // Subject

MailMessage. Body = "content ";

MailMessage. BodyEncoding = Encoding. UTF8; // body Encoding

MailMessage. IsBodyHtml = true; // set it to HTML Format

MailMessage. Priority = MailPriority. Low; // Priority

  Note: you must first set EnableSsl and usedefacrecredentials, and then instantiate the Credentials.