What should I use?

Hi all. In the past I have usually built websites in Flash, using Dreamweaver only to embed the file. I have a new site that I am going to make, the idea is extremely simple,but I am unsure which is the best path to go down.

The website will allow people to upload a small file, and then email it through the site to a series of (pre) selected destinations. To clarify, the user will upload their file, then select from a bullet-point list of about 30 different destinations where they want the file to go, hit 'send' and the file will email to the destinations they have selected.
The file uploaded does not need to remain on the website/server any longer than it takes to send the email.

I have reasonable knowledge of HTML and Flash, but aside from that I'm pretty pants. I want the email to send through an online server (not simply by using Outlook), so I'm going to have to wrap my head around how this works.

My question is: To achieve this sort of site, what is the best path to go down? And is there anything in particular I will need to know?

I do not expect anyone here to coach me through this, but if someone could point me in the most logical direction then I will go and do some reading.

Thank you in advance, I coudl really do with some help on this!

Nathan