Fortunately 9-digit zip codes are not that precise. They represent a sub-area within the 5-digit area. I have used a similar trick to get around the zip code qualifier ... search for the town hall or county courthouse address and use that zip code in your email.
But as other commenters have said, most emails are never seen much less read by the addressed congress-critter. A cipher in their office reads it, harvests the return email address for (unending) funding requests, and then the email is destroyed.
When I worked in NYC I learned that one zip code covered just the one building where I worked … and our four-digit zip code extension corresponded to our office suite number in the building.