title: How do I send emails outside my domain with Exchange 2007 and c#
body: <p>I am able to send emails using the typical C# SMTP code across Exchange 2007 as long as both the from and to addresses are within my domain.</p>
  
  <p>As soon as I try to send emails outside the domain I get:</p>
  
  <p>Exception Details: System.Net.Mail.SmtpFailedRecipientException: Mailbox unavailable. The server response was: 5.7.1 Unable to relay</p>
  
  <p>How can I get exchange to accept my email and send it out to the internet?</p>