C# E-mail Client Mails Not Received

[cnixuser]

Hi, I am trying to write an application that will e-mail sales data reports once per day. I have largely succeeded in creating the application and I am able to e-mail my reports to some e-mail addresses such as gmail ones ;however, when attempting to send e-mails to addresses on my companies internal server the e-mails never arrive. I was wondering if anyone knew what could allow gmail addresses to receive e-mails from my application, but not allow other servers to receive mail from my application, below is the portion of code doing the e-mailing:

        public string SendEmail()
        {
            try
            {
                using (System.Net.Mail.MailMessage message = new System.Net.Mail.MailMessage(EmailFrom, EmailTo))
                {
                    message.Subject = ConfigurationManager.AppSettings["emailSubject"].ToString();
                    message.Body = ConfigurationManager.AppSettings["emailMainBody"].ToString() + "\n\nSent On:\n" + DateTime.Now.ToString() + "\n" + SerialPortCommands.RemoveControlCharacterPairs(SerialPortCommands.Asciireport);
                    //System.Net.Mail.SmtpClient Client = new System.Net.Mail.SmtpClient("localhost");
                    System.Net.Mail.SmtpClient Client = new System.Net.Mail.SmtpClient("127.0.0.1");
                    Client.DeliveryMethod = System.Net.Mail.SmtpDeliveryMethod.PickupDirectoryFromIis;
                    Client.Send(message);
                    Thread.Sleep(2000);
                }
                return null;
            }
            catch (Exception ex)
            {
                Log.WriteToLog(ex);
                return "Error Code: email-1";
                Application.Restart();
            }
        }

And here are the relevant portions from my App.Config file:

<add key="ToAddress" value="[e-mail]"/>
    <add key="FromAddress" value="[e-mail]"/>
    <add key="emailSubject" value="==DEX Collector Message== Your Dex Report Has Been Sent"/>
    <add key="emailMainBody" value="Vending Machine DEX Data"/>
    <add key="MessageSendTime" value="1:17:00 PM"/>

any help would be greatly appreciated, as I am quite stumped :)

[Plater]

Well technically no, because I built my own SMTPClient as I disliked the built in one.
But yes, I *DO* send the authentication information to the mail server, my mail server won't send emails out unless you are a valid user.

[cnixuser]

Well technically no, because I built my own SMTPClient as I disliked the built in one.
But yes, I *DO* send the authentication information to the mail server, my mail server won't send emails out unless you are a valid user.

Have you had success sending to e-mail accounts hosted on goDaddy servers?

[Plater]

Have you had success sending to e-mail accounts hosted on goDaddy servers?

I have not had any failures that I have seen.

[cnixuser]

I have not had any failures that I have seen.

I just can't figure out what it could be. I am able to send to gmail just fine without using credentials.

[Plater]

I just can't figure out what it could be. I am able to send to gmail just fine without using credentials.

And I we all keep telling you that you need to use credentials.
There really shouldn't be anything difficult to grasp on this concept.
Have you even tried to use valid credentials?

[cnixuser]

And I we all keep telling you that you need to use credentials.
There really shouldn't be anything difficult to grasp on this concept.
Have you even tried to use valid credentials?

I tried using credentials from my gmail account yes "username" and "password", and when that didn't work, I tried "username@gmail .com", and "password".

[Plater]

Ok now I don't know what you were doing.
You would not be able to send ANY email through gmail's mail servers without authenticating and using SSL, so you are probably using your company's mail server to send the mail. You must provide a valid login for THAT server in order to send emails successfully.

[cnixuser]

Ok now I don't know what you were doing.
You would not be able to send ANY email through gmail's mail servers without authenticating and using SSL, so you are probably using your company's mail server to send the mail. You must provide a valid login for THAT server in order to send emails successfully.

Well, I'm actually sending from the pc that I am running the application from. I set the SmtpClient as the local host (127.0.0.1). The pc is on a network independent from the one at work (a Verizon cellular modem). I do honestly have a misunderstandin g of how to use credentials. With my new description, do you believe still that I need the credentials for the server at my company which I would be sending to and not from?

[cnixuser]

Well, I'm actually sending from the pc that I am running the application from. I set the SmtpClient as the local host (127.0.0.1). The pc is on a network independent from the one at work (a Verizon cellular modem). I do honestly have a misunderstandin g of how to use credentials. With my new description, do you believe still that I need the credentials for the server at my company which I would be sending to and not from?

It occurs to me that if I had my SmtpClient as the localhost, I would have to alter some settings for my IIS virtual SMTP server, so that it was configured for authentication rather than anonymous access, and then in my code, add the credentials to my localhost's IIS virtual SMTP server. Plater, is this what you were trying to tell me to have authenticated? If so, I apologize for being too dense :)

[Plater]

Hmmm no. It had actually not occured to me that you could be using localhost to send the emails. Will the final product be run in the same manor?

The crenedtials supplied are for the server you are sending mail from. so if you are sending mail from a localhost, I now understand your confusion about what credentials to send.
That being said there are a number of other things in the SMTP protocol that could cause your emails to be rejected. It's possible that godaddy implents the part of the protocol that says there needs to be a valid MX record for the address that is SENDING the messages.
i.e. it needs to be able to go -> somename@somedo main.com....che cking the lookup for somedomain.com
They may also go the next step which would be reverse validation and attempt to verify that someuser is a valid username in somedomain.com

and it could also be none of those and something else entirely.
Your best bet might be to get in touch with whoever handles your email and see if they can find anything in the logs about why your messages are rejected