For example, some hypothetical person likes to send all her emails in bright green font and in bold and italics (incredibly difficult to read). When this person sends a post to DorothyL, the HTML (to make the green, bold and italics) gets sent with it. Some DorothyLers will receive the entire digest in green, bold and italics because this one person sent HTML-encoded email to the listserv. It's a mess and extremely difficult to read.
Please be considerate of other DorothyLers and ensure that the messages you send to DorothyL are in PLAIN TEXT, not HTML. Below is a web site with instructions on configuring your email client to send plain text and not HTML.
Configuring email Clients to Send Plain ASCII Text