Outlook Express offers two formats for sending e-mail messages: HTML and plain text. HTML is the same format that is used to display Web pages. If you intend to include pictures inside your e-mail messages or view pictures that others send you, you must opt for HTML format. HTML-formatted messages take longer to transmit, and some e-mail software doesn't accept them. In plain-text format, only numbers and letters are transmitted.
Follow these steps to choose a default mail-sending format:
Choose Tools, Options.
You see the Options dialog box.
Select the Send tab.
Under Mail Sending Format, select the HTML or Plain Text option button.
Click the OK button.
No matter which format you choose, you can send a particular e-mail message in the HTML or plain-text format. In the New Message window, choose Format, Rich Text (HTML) or Format, Plain Text.