For example, Use HTML, to make the content of the message bold red-colored text.   You can Google this issue to learn how to do this in PHP.  It might (or might not be helpful) to examine the message details icon in one of your opened emails to see its email header. This is a bit unpredictable but for text only it might have: Content-Type: text/plain.  To send HTML tags you have to make sure the message header is: Content-Type: text/html; charset="iso-8859-1".  You can set these headers in PHP for the mail function.  Check out the online PHP manual for where and how to define these and also refer to the IT 202 manual.