An envelope layout is a special type of Statement Designer page layout used for creating customized envelopes to be printed with statements. Envelope layouts work just like page layouts, with two notable exceptions:

Envelope layouts are easily distinguishable from other page layouts in the Layout Tree by their unique envelope icons. When selecting a page layout in the Envelope field of the Layouts tab in Statement Templates, only envelope layouts appear in the list of available page layouts.

See also:   Adding an Envelope Layout
  Renaming or Deleting a Page Layout
  Page Layout
  Tabs3 Sample Reports