Win Server 2008 R2 and Mail Enable

[frikkie6000]

Hi guys

I am hosting a c# app in a win dedicated environment this is also the mail server so I make use of Mail Enable

I am currently authenticating in my app sending of mails via server with a username and password but noticed with telkomsa.net and vodamail.co.za email addresses I get the following error in Mail Enable

The socket connection to the remote host failed. The host was either not contactable or it rejected your connection

Has someone perhaps experienced this ? Or can someone perhaps recommend an alternative

My code as follow

mailClient.Host = "(IP Here)";
mailClient.EnableSsl = false;
mailClient.Port = 25;
mailClient.UseDefaultCredentials = false;
mailClient.Credentials = new NetworkCredential("(username)", "(password)");