Easy to bypass SMTP server body verification

Due to technical and security issues, most of the virtual host service providers now use the JMail component to provide ASP script to send mail services, the sending code is as follows:
Set JMail = Server.CreateObject ("Jmail.smtpmail")
jmail.serveraddress = "SMTP Server Address"
Jmail.sender = "Sender mail Address"
Jmail.subject = "message subject"
Jmail.addrecipient "Recipient email Address"
Jmail.body = "message body"
jmail.priority = 1
Jmail.execute the SMTP server that is set up requires authentication, such as a smtp.21cn.com server, which only allows sending mail addresses to be *@21cn.com messages, so it is not possible to send all messages freely.
So, I thought of a way: Try to cheat the SMTP server. Write the ASP send code as follows:
Set JMail = Server.CreateObject ("Jmail.smtpmail")
jmail.serveraddress = "Smtp.21cn.com"
Jmail.sender = "Myside@21cn.com"
Jmail.subject = "message subject"
Jmail.addrecipient Recipient Email Address
Jmail.body = "The sending address of this message is:" & "The True Mail Sender address" & ", if you want to reply this email, please send to" & "the True Mail Sender address" & vbCrLf & "message body
jmail.priority = 1
Jmail.execute so every time send mail, smtp.21cn.com server is thought to be myside@21cn.com send mail, so can pass the verification smoothly. When the recipient receives the message, it appears in the first line of the body of the message "The sending address of this message is: (The real address), if you want to reply to this message, please send to (the real address)" such text. Detailed send the page source code please click here to download.