[3.0/LINQ] SMTP fails someof the time

Okay i got a weird one for you

we have a open smtp server here in the building for sending out alerts and whatnot

I can send from my machine and get an email
My cube mate can send from his machine and i get the email ( they are currently all addressed to me)

If i log on to a machine in my computer lab it doenst work for me
If i other people from my same group ( that have the same AD permissions) with the exception of the one guy they get an error

Code:

System.Net.Mail.SmtpException: Failure sending mail. ---> System.Net.WebException: Unable to connect to the remote server ---> System.Net.Sockets.SocketException: An established connection was aborted by the software in your host machine 10.209.xx.xx:xx

Here is the code i am using
C# Code:
private static void UsatSendMail(string[] To, string From, string Subject, string Message)
        {
            SmtpClient server = new SmtpClient("usat-xxxxx");
            server.Credentials = new NetworkCredential("user", "pass");
            MailMessage email = new MailMessage();
            email.From = new MailAddress(From);
            foreach (string T in To)
            {
                email.To.Add(T);
            }
            email.Subject = Subject;
            email.Body = Message;
            try
            {
                server.Send(email);
                MessageBox.Show("Page Sent");
            }
            catch (SmtpFailedRecipientException error)
            {
                MessageBox.Show("error: " + error.Message + "\nFailing recipient: " + error.FailedRecipient);
                //LogFile();
            }
 
            catch (Exception ex)
            {
                MessageBox.Show(ex.Message);
                //LogFile();
            }
Ive also tried making it a clickonce install package to insure the other people have all the nesscary pre reqs ( .net3.5)

I'm really at a loss as to why it works in some situations and not in others.

If anyone has any idea on what i could look for that might explian this That would be really helpful.