 <p><a href="http://en.wikipedia.org/wiki/Signature_block#E-mail_and_Usenet" rel="nofollow">http://en.wikipedia.org/wiki/Signature_block#E-mail_and_Usenet</a> gives an overview about email signatures. As guys already mentioned, signature is just a part of the email body. The only restrictions are: "<em>it should be delimited from the body of the message by a single line consisting of exactly two hyphens, followed by a space, followed by the end of line (i.e., "-- \n")</em>".</p>