The Insert stamp in body action inserts a block of text into the message body. The stamps are maintained as named objects in the database and are selected from a list. The stamp definitions contain the text of the stamp (which can contain Hosted Email Security tokens/variables), whether they are to be inserted at the beginning or the end of the message body, and whether or not to avoid stamping TNEF and digitally signed messages to prevent breakage.
Hosted Email Security recognizes messages signed using the S/MIME standard.
See Configuring Stamps.