I have purchased an authenticated SMTP package with my hosting company.

I have tested the account settings via Outlook 2010 successfully.

Outlook settings:

**Email**: me@domain.com
**Outgoing SMTP**: smtp.hostingcompany.net

**Logon Info:**

* **user**: mydomain.com\_account
* **pass**: password

**More Settings > Outgoing Server:**

* My Outgoing Server (SMTP) Requires authentication
* **User**: mydomain
* **Pass**: password

I have tried all possible combinations when specifying the NetworkCredentials and I keep getting an **SMTP Exception**: "Faulure Sending Email"
**InnerException**: Invalid length for a Base-64 char array.

```
public static void SendEmail(string To, string Subject, string Body)
    {
        try
        {
            using (SmtpClient mySmtpClient = new SmtpClient(GlobalSettings.EmailHost))
            {
                mySmtpClient.UseDefaultCredentials = false;
                //mySmtpClient.EnableSsl = false;
                mySmtpClient.Credentials = new NetworkCredential(mydomain.com_account, GlobalSettings.EmailPassword);

                MailAddress from = new MailAddress("email@mydomain");
                MailAddress to = new MailAddress(To);

                using (
                    MailMessage myMail = new MailMessage(from, to)
                    {
                        Subject = Subject,
                        SubjectEncoding = Encoding.UTF8,
                        Body = Body,
                        BodyEncoding = Encoding.UTF8,
                        IsBodyHtml = true
                    })
                {
                    mySmtpClient.Send(myMail);
                }
            }
        }
        catch (SmtpException ex)
        {
            Log.WriteLog(string.Format("[Send Mail Exception] --> SMTPException has occurred: {0}", ex.Message), LogLevel.Error);
        }
        catch (Exception ex)
        {
            Log.WriteLog(string.Format("[Send Mail Exception] --> Exception has occurred: {0}", ex.Message), LogLevel.Error);
        }
    }

```

I have tried three possible username login parameters for the NetworkCredential(). 

Thanks in advance.

**EDIT: NTLM Hack**

I added the following lines to my code:

```
FieldInfo transport = _client.GetType().GetField("transport",
    BindingFlags.NonPublic | BindingFlags.Instance);

FieldInfo authModules = transport.GetValue(_client).GetType()
    .GetField("authenticationModules",
        BindingFlags.NonPublic | BindingFlags.Instance);

Array modulesArray = authModules.GetValue(transport.GetValue(_client)) as Array;
modulesArray.SetValue(modulesArray.GetValue(2), 0);
modulesArray.SetValue(modulesArray.GetValue(2), 1);
modulesArray.SetValue(modulesArray.GetValue(2), 3);

```

I am now getting a new message:

```
Mailbox unavailable. The server response was: relay not permitted

```