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.
The solution mentioned by willaien resolved this issue. Namely, using SecureSocketOptions.StartTls
instead of SecureSocketOptions.SslOnConnect
.
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