fix typo

Doc/tut/tut.tex

@@ -4781,7 +4781,7 @@ packages. For example:
   Despite the modules names, no direct knowledge or handling of XML is needed.
 \item The \ulink{\module{email}}{../lib/module-email.html} package is a library
   for managing email messages, including MIME and other RFC 2822-based message
-  documents. Unlike \module{smptlib} and \module{poplib} which actually send
+  documents. Unlike \module{smtplib} and \module{poplib} which actually send
   and receive messages, the email package has a complete toolset for building
   or decoding complex message structures (including attachments) and for
   implementing internet encoding and header protocols.