I think this should be "versionchanged", not "versionadded"
diff --git a/Doc/library/smtplib.rst b/Doc/library/smtplib.rst
index 4805c8e..cfd5018 100644
--- a/Doc/library/smtplib.rst
+++ b/Doc/library/smtplib.rst
@@ -45,7 +45,7 @@
     (250, b'Ok')
     >>>
 
-   .. versionadded:: 3.3
+   .. versionchanged:: 3.3
       Support for the :keyword:`with` statement was added.