Codeigniter Project - Send HTML and Plain Text Emails

This should be a simple task. I've got a Codeigniter project which sends emails from the site to various people (precisely who varies according to the button clicked, I'll let you have a list if you're awarded the project but they're all set in a database or config file) I need the emails to be sent as both HTML and plain text - at the moment, they're only being sent as HTML and that doesn't display properly in all email programs. The emails need to include links as well as the message sent & the user name/email and a sensible subject line - I'll provide the precise format but it's quite close at the moment so there's nothing major to change. It would make sense for longer term maintainability if the message sending was all in one routine with just different parameters according to which button was clicked - I think the code is close to that already but you'll need to check and amend if not. Message me on this site to see the current site. You'll get FTP access when the project is awarded.