Adding Required to drop-down

Hi,
How would add a required * element to this field. It’s a dropdown of emails with pipes, and I want to make it a mandatory selection. I’ll probably have to add a general first line before the “Estimates”, something like, “make your selection”

Where do I add the *, and what additional code do I need?
Thanks so much.

<p>Send my Inquiry
to the Following Dept.*
[select your-recipient “Estimates & Sales|dsmith@dasecoelectrical.com”
“Customer Service|lobrien@dasecoelectrical.com”
“Marketing|arossi@dasecoelectrical.com”]

http://wordpress.org/plugins/contact-form-7/