Hi Michael,

Currently the code is like this line 633 in Email.cs:

if (smtpSettings.RequiresAuthentication)
                {
                    NetworkCredential smtpCredential
                        = new NetworkCredential(
                            smtpSettings.User,
                            smtpSettings.Password);

                    smtpClient.Credentials = smtpCredential;
                }

can you try add

else
{
  smtpClient.UseDefaultCredentials = true;
}

and see if that solves the problem?

Hope it helps,

Joe