Added smtplib.py (thanks, Guido!).
diff --git a/Doc/lib/libundoc.tex b/Doc/lib/libundoc.tex
index 0db5e8c..b63574d 100644
--- a/Doc/lib/libundoc.tex
+++ b/Doc/lib/libundoc.tex
@@ -47,6 +47,9 @@
 
 \item[poplib.py]
 --- Post Office Protocol client by Dave Ascher.
+
+\item[smtplib.py]
+--- Simple Mail Transfer Protocol (SMTP) client code.
 \end{description}