Send SMTP email testing Microsoft Office 365 in .net

Question

i have a mail account on the Exchange Online service. Now i'm trying to test if i am able to send mails to customers ( on varoius domains and on Microsoft Office 365) through c# application

I tried implementing the below code but i am getting the error

"The remote certificate is invalid according to the validation procedure."

MailMessage mail = null;                
mail = new MailMessage();

string[] strToList = "[email protected]"              
foreach (string strID in strToList)
{
    if (strID != null)
    {
        mail.To.Add(new MailAddress(strID));
    }
}

mail.From = "[email protected]";
mail.Subject = "testing"
mail.IsBodyHtml = true;
mail.Body = "mail body";

SmtpClient client = new SmtpClient("smtp.outlook.office365.com");
client.Port = 587;
client.EnableSsl = true;
client.UseDefaultCredentials = false;
NetworkCredential cred = new System.Net.NetworkCredential("[email protected]", "mypassword");
client.Credentials = cred;
client.Send(mail);

Please advice if i am doing anything wrong. Thanks a lot in advance.

Answer 1

this works for me ( edited from source )

   ThreadPool.QueueUserWorkItem(t =>
            {
                SmtpClient client = new SmtpClient("smtp.office365.com",587);
                client.EnableSsl = true;
                client.Credentials = new System.Net.NetworkCredential("[email protected]", "password");
                MailAddress from = new MailAddress("[email protected]", String.Empty, System.Text.Encoding.UTF8);
                MailAddress to = new MailAddress("[email protected]");
                MailMessage message = new MailMessage(from, to);
                message.Body = "The message I want to send.";
                message.BodyEncoding = System.Text.Encoding.UTF8;
                message.Subject = "The subject of the email";
                message.SubjectEncoding = System.Text.Encoding.UTF8;
                // Set the method that is called back when the send operation ends.
                client.SendCompleted += new SendCompletedEventHandler(SendCompletedCallback);
                // The userState can be any object that allows your callback 
                // method to identify this send operation.
                // For this example, I am passing the message itself
                client.SendAsync(message, message);
            });

        private static void SendCompletedCallback(object sender, AsyncCompletedEventArgs e)
        {
            // Get the message we sent
            MailMessage msg = (MailMessage)e.UserState;

            if (e.Cancelled)
            {
                // prompt user with "send cancelled" message 
            }
            if (e.Error != null)
            {
                // prompt user with error message 
            }
            else
            {
                // prompt user with message sent!
                // as we have the message object we can also display who the message
                // was sent to etc 
            }

            // finally dispose of the message
            if (msg != null)
                msg.Dispose();
        }