You'd want to do is establish the To: address as a variable (such as $sendee) that you can assign a value to it from your dropdown menu options. Once you have that dropdown menu variable established, carry it over to the processing script with the rest of the form field values.
For the script itself, you could use something like http://www.dtheatre.com/scripts/formmail.php .. If you use this script, you could take what they give you for the $recipient line in the formmail.php and change it from:
Then establish the variable assigned to the dropdown menu items as $sendee. Once you choose one, that value would be carried over to the formmail.php file. You'll need to do a bit of haxoring to make it work but it's doable.
I can't vouch for all related security issues involved with using this script. It was just an example of one that you could use. :-)
Yep, I was pretty much going to echo what Bill said. It should be fairly easy to use just about any php form mail script (I personally prefer phpmailer, http://phpmailer.sourceforge.net/) and just adjust the recipient email address based on the contents of the dropdown in the form.
So for example using your emails from below, in the handler for the form you'd do something like:
It took a lot of searching, but I finally settled on this form processor because a) it's a breeze to configure, b) it's easy to customize (I have almost zero PHP programming experience, and I was able to turn it into an invoice generator), c) it handles attachments, and d) it is very secure.