如何从 ASP.Net/C# Webforms 中的任何 Email 地址发送 email

Question

I am a beginner programmer in C#, I want to create a contact form, where the user can enter any email address as the "From" address, and they can send a message. Every time it sends, it says the "From" address is the credentials that I am using. How do I change the From address to the address based on the user's input like any other contact form. Should I use a different Smtp Server? Thanks

    protected void sendbttn_Click(object sender, EventArgs e)
    {
        try
       {



            MailMessage message = new MailMessage();
            message.From = new MailAddress(fromtxt.Text);
          
            message.To.Add("toEmail");
            message.Subject = "Subject: " + subjecttxt.Text;
            message.Body = mesgtxt.Text;
            message.IsBodyHtml = true;

            SmtpClient smtpClient = new SmtpClient();
           
           smtpClient.Host = "smtp.gmail.com";
           smtpClient.Port = 587;

        smtpClient.UseDefaultCredentials = false;
            
           smtpClient.Credentials = new System.Net.NetworkCredential("Credemail", "Credpassword");
           
            smtpClient.EnableSsl = true;
            smtpClient.Send(message);
            MessageBox.Show("Your email has been sent!");

            fromtxt.Text = "";
            subjecttxt.Text = "";
            mesgtxt.Text = "";
        }

        catch
        {
            MessageBox.Show("Something went wrong, please try again");
        }

Answer 1

If your host is not registered as official mail provider, you should never even think about sending E-Mail in the name of somebody else.

Instead use a dedicated address as sender and to authenticate at the smart host and remember to store the credentials in a save location so nobody can "adopt" them - the program sourcecode as in the example is definitely not a save place, store them in IIS property fields.

The address entered in the form may be used as reply-to and possibly as the senders display name.

The body will not be html, too. The property therefore should be 'false'.

string credMail = "example@gmail.com";
string credPasswd = "example_p@asswd";

MailMessage message = new MailMessage();
message.From = new MailAddress(credMail,fromtxt.Text);
message.To.Add("toEmail");
message.Subject = "Subject: " + subjecttxt;
message.Body = mesgtxt.Text;
message.IsBodyHtml = false;
message.ReplyToList.Add(fromtxt.Text);

SmtpClient smtpClient = new SmtpClient();
smtpClient.Host = "smtp.gmail.com";
smtpClient.Port = 587;
smtpClient.UseDefaultCredentials = false;
smtpClient.Credentials = new System.Net.NetworkCredential(credMail, credPasswd);
smtpClient.EnableSsl = true;
smtpClient.Send(message);
MessageBox.Show("Your email has been sent!");