Index: System.Net.Mail/SmtpClient.cs
===================================================================
--- System.Net.Mail/SmtpClient.cs       (revision 73032)
+++ System.Net.Mail/SmtpClient.cs       (working copy)
@@ -400,7 +400,9 @@
 
                private void SendData (string data)
                {
-                       writer.WriteLine (data);
+                       writer.Write (data);
+                       // Certain SMTP servers will reject mail sent with unix line-endings; see http://cr.yp.to/docs/smtplf.html
+                       writer.Write ("\r\n");
                        writer.Flush ();
                }
 
@@ -555,7 +557,9 @@
 
                private SmtpResponse SendCommand (string command)
                {
-                       writer.WriteLine (command);
+                       writer.Write (command);
+                       // Certain SMTP servers will reject mail sent with unix line-endings; see http://cr.yp.to/docs/smtplf.html
+                       writer.Write ("\r\n");
                        writer.Flush ();
                        return Read ();
                }