Outlook features three forrmats for composing messages. "Rich Text," which is often the default setting, allows for formatting of messages (font, color, size, etc.), but does not allow the recipient to preview attachments within Outlook. Because of this limitation, we recommend that users use one of the other two options: HTML or Plain Text. HTML allows formatting and allows attachments to be previewed in Outlook. Plain Text does not allow formatting - which leads to smaller e-mails - and also allows for attachments to be previewed.