An envelope provides the integration of the functionality of an email application program and the functionality of a document editor so that a sender can send introductory text to the recipient of an email message constituting a document without corrupting the original document. Users of document editors can generate and edit documents for email transmission by first creating the document with the document editor and then invoking an envelope to send the document as the message body with introductory text. The envelope has its own user interface that is fully functional within the confines of the document editor's user interface to provide the user with the functionality of the email client application program. The envelope includes an introduction field for the entry of introductory text by the sender. The introduction field in the envelope is a rich edit control in plain text mode, similar to the subject field of the envelope. When the user sends the document, the document editor prepends the introductory text to the body of the message. The document editor then converts the introductory text and the body of the document to an HTML message, and the email client sends the email message to the recipient.