Post by Email & Categories

On my website, I’m setting up a form that allows users to submit an event or “happening” in my local area. That form will then automatically post (post by email style) to the main page via a blog section. Is it possible to provide a drop down menu of categories or tags in the form that then allows the post to not only post on the main page, but also on the specific category page for that category they select? Does that make sense?