Are you looking at adding a complete email solution or just a script to send email. If it is just a script, I am sure that you can find something on the web and probably in the code snippet archive. If you are looking for an email solution....I would recommend www.globalsend.com It is a complete email solution for a very very low cost. $5 per user, per month. There is a minimum of 5 user per domain. There is a setup fee but it is only $100. There is a webmail interface, pop access, WAP, you name it, it is there. There is a nice web interface for administering users,colors,logos, just about anything on the site.
The nice thing about this service is that you don't have to worry about the hardware or anything like that, they take care of everything. This is probably more than what you are looking for but then again, maybe not.
