Use multipart email messages to send email content in both plain text and HTML format.
Email is another interface to your web application. Ideally, you want that interface (and any other, be it a phone or a handheld device) to be as full-featured as the one you provide through a web server. While this isn't always possible, it's a good goal to keep in mind, and it will help push you to create better user interfaces.
This hack describes how to send email using a multipart construction, where one part contains a plain-text version of the email and the other part is HTML. If your customers have HTML email turned off, they will still get a nice email, even if they don't get all of the HTML markup.
Figure 2-13 shows some different forms of mail messages. On the lefthand side is the simplest form of mail, the text message. At the top of the email is the header, which defines the subject, whom the mail is from, whom the mail is going to, and so on. These are followed by a carriage return, and finally, the message text.
Figure 2-13. Different mail forms
The emails in the middle and on the right in Figure 2-13 are multipart messages. The header remains much the same as with the text message, with the exception that some information about the multiple parts is included. The text is then placed within a part, and the HTML is placed in another part.
This way, mailers can decide ...