向多个地址发送雅虎电子邮件

    string smtpAddress = "smtp.mail.yahoo.com";
    int portNumber = 587;
    bool enableSSL = true;
    string emailFrom = "mitshel@yahoo.com";
    string password = "xxxxxx!";
    List<string> emailToList = new List<string>;
    emailToList.Add("dimitris.chris@yahoo.com");
    //add as many other as you like 
    string subject = "Hello";
    string body = "Hello, I'm just writing this to say Hi!";
    using (MailMessage mail = new MailMessage())
    {
        mail.From = new MailAddress(emailFrom);
        foreach(string recipient in emailToList){
            mail.To.Add(recipient);
        }
        mail.Subject = subject;
        mail.Body = body;
        mail.IsBodyHtml = true;
        // Can set to false, if you are sending pure text.

        using (SmtpClient smtp = new SmtpClient(smtpAddress, portNumber))
        {
            smtp.Credentials = new NetworkCredential(emailFrom, password);
            smtp.EnableSsl = enableSSL;
            smtp.Send(mail);
         }

或

    string smtpAddress = "smtp.mail.yahoo.com";
    int portNumber = 587;
    bool enableSSL = true;
    string emailFrom = "mitshel@yahoo.com";
    string password = "xxxxxx!";
    List<string> emailToList = new List<string>;
    emailToList.Add("dimitris.chris@yahoo.com");
    //add as many other as you like 
    string subject = "Hello";
    string body = "Hello, I'm just writing this to say Hi!";
    foreach(string recipient in emailToList){
    using (MailMessage mail = new MailMessage())
    {
        mail.From = new MailAddress(emailFrom);
        mail.To.Add(recipient);
        mail.Subject = subject;
        mail.Body = body;
        mail.IsBodyHtml = true;
        // Can set to false, if you are sending pure text.

        using (SmtpClient smtp = new SmtpClient(smtpAddress, portNumber))
        {
            smtp.Credentials = new NetworkCredential(emailFrom, password);
            smtp.EnableSsl = enableSSL;
            smtp.Send(mail);
         }
}

我假设您有一个包含多个电子邮件地址的字符串，由逗号和空格分隔，例如

string emailTo = "someEmail@email.com, someEmail2@email.com, someEmail3@email.com";

您需要将emailTo分隔为字符串集合。要做到这一点，您可以使用以下命令:

// Separate the emailTo string into a list of email addresses
List<string> emailAddresses = new List<string>();
    int startingIndex = 0;
    while (startingIndex < emailTo.Length)
    {
        int commaIndex = emailTo.IndexOf(",", i);
        if (commaIndex != -1)
        {
            //Extract the email address
            string emailAddress = emailTo.Substring(startingIndex, commaIndex - startingIndex);
            // Remove the space following the comma
            if (emailAddress.Substring(0, 1) == " ")
            {
                emailAddress = emailAddress.Substring(1, emailAddress.Length - 1);
            }
            i = startingIndex + 1;
            result.Add(emaiAddress);
        }
    }
// Add each email address to the message's recipients
foreach(string emailAddress in emailAddresses)
{
    mail.To.Add(emailAddress);
}

这种方法的好处是，你不需要手动解析电子邮件地址，并在你有一个emailTo字符串，其中包含许多电子邮件地址添加到收件人列表自己。