Was the drop down field made with the SilverStripe Form? or was it something you coded yourself?

If it was the SS Form, then you can go to the SS admin, click the page where the form is, click the "Submissions" tab. Also, if you go to the "Form" tab, you should be able to enter an email for the submissions to also be sent to.

If you coded the form yourself, you might need to change how the value is being sent. If you are sending it in an email, or posting it to a file, or some other method. Check to make sure that the value is correctly being pulled when the form is submitted. Then check to see what happens to the value after its pulled.

I can help you more with this if you need "Exact" help.