Update readme.

README.md

@@ -12,12 +12,21 @@ Usage:
 
 ## Example usage
 
-Run:
+In the `example` folder, there is an example centos container than can be used to test connectivity.
     
     cd example
     docker build -t example .
     docker run --rm -it --link=postfix:postfixcontainer example
     
-    mail test@example.com
+    # from commandline:
+    $ mail test@example.com
     
-    # mail should be sent by the postfix container
+    # from an application, python:
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+    $ python
+    Python 2.6.6 (r266:84292, Jan 22 2014, 09:42:36) 
+    [GCC 4.4.7 20120313 (Red Hat 4.4.7-4)] on linux2
+    Type "help", "copyright", "credits" or "license" for more information.
+    >>> import smtplib
+    >>> s = smtplib.SMTP('postfixcontainer')
+    >>> s.sendmail('test@example.eionet.europa.eu', ['user@example.com'], 'test')
+    {}
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