SmtpClient.Send не работает в среде Linux

Следующий код, написанный в среде .net core 2, работает в среде the windows environment, но не в среде the linux environment.

string host = "10.99.99.10";
int port = 25;
string userName = "[email protected]";
string password = "password";
string from = userName;

var client = new SmtpClient
{
    Host = host,
    Port = port,
    EnableSsl = false,
    DeliveryMethod = SmtpDeliveryMethod.Network,
    UseDefaultCredentials = false,
    Credentials = new NetworkCredential(userName, password)
};

MailMessage mailMessage = new MailMessage();
mailMessage.From = new MailAddress(from);
mailMessage.To.Add(userName);
mailMessage.Body = "This is test mail.";
mailMessage.Subject = "Testing";                
client.Send(mailMessage);

Исключение: Failure sending mail.

Внутреннее исключение:

System.ComponentModel.Win32Exception (0x80004005): GSSAPI operation failed with error - An invalid status code was supplied (Unknown error).
   at System.Net.Security.NegotiateStreamPal.AcquireCredentialsHandle(String package, Boolean isServer, NetworkCredential credential)
   at System.Net.NTAuthentication.Initialize(Boolean isServer, String package, NetworkCredential credential, String spn, ContextFlagsPal requestedContextFlags, ChannelBinding channelBinding)
   at System.Net.Mail.SmtpNtlmAuthenticationModule.Authenticate(String challenge, NetworkCredential credential, Object sessionCookie, String spn, ChannelBinding channelBindingToken)
   at System.Net.Mail.SmtpConnection.SetContextAndTryAuthenticate(ISmtpAuthenticationModule module, NetworkCredential credential, ContextAwareResult context)
   at System.Net.Mail.SmtpConnection.GetConnection(String host, Int32 port)
   at System.Net.Mail.SmtpTransport.GetConnection(String host, Int32 port)
   at System.Net.Mail.SmtpClient.GetConnection()
   at System.Net.Mail.SmtpClient.Send(MailMessage message)

Трассировки стека:

at System.Net.Mail.SmtpClient.Send(MailMessage message)
   at MyProject.Helper.Utils.SendMail() in C:\Test\MyProject\MyProject.Helper\Utils.cs:line 146

Линукс: Ubuntu 16.04.3 LTS

Это консольное приложение. Почему не работает в среде Linux?