I'm getting a MailKit.Security.SslHandshakeException when trying to connect to "smtp.office365.com"
I am trying to use MailKit to send an email message via "smtp.office365.com". Here is the code I'm using.
using (var client = new SmtpClient(new ProtocolLogger("smtp.log")))
{
client.ServerCertificateValidationCallback = (s, c, h, e) => true;
client.Connect("smtp.office365.com", 587, SecureSocketOptions.SslOnConnect);
client.Authenticate(new SaslMechanismNtlmIntegrated());
Debug.WriteLine(client.IsAuthenticated);
client.Send(message);
client.Disconnect(true);
}
The SaslMechanismNtlmIntegrated class I got from this comment on GitHub.
Whenever I run this code, I get an SslHandshakeException.
Here are the details of the exception:
MailKit.Security.SslHandshakeException
HResult=0x80131500
Message=An error occurred while attempting to establish an SSL or TLS connection.
One possibility is that you are trying to connect to a port which does not support SSL/TLS.
The other possibility is that the SSL certificate presented by the server is not trusted by the system for one or more of the following reasons:
1. The server is using a self-signed certificate which cannot be verified.
2. The local system is missing a Root or Intermediate certificate needed to verify the server's certificate.
3. The certificate presented by the server is expired or invalid.
See https://github.com/jstedfast/MailKit/blob/master/FAQ.md#InvalidSslCertificate for possible solutions.
Source=MailKit
StackTrace:
at MailKit.Net.Smtp.SmtpClient.<ConnectAsync>d__70.MoveNext()
at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
at MailKit.Net.Smtp.SmtpClient.Connect(String host, Int32 port, SecureSocketOptions options, CancellationToken cancellationToken)
at QuoteAndOrder.SpecialsQuoteWindow.BtnEmail_Click(Object sender, RoutedEventArgs e) in SpecialsQuoteWindow.xaml.cs:line 501
Inner Exception 1:
IOException: The handshake failed due to an unexpected packet format.
I went to the FAQ mentioned in the details, but the workaround given did not resolve the issue.