Many congresscritters don't have public email addresses -- instead, they have hard-to-locate webforms that slow down activist email campaigns and make it harder for constituents to get in touch. EFF and the Sunlight Foundation has fixed this, giving every member of Congress her or his own email address -- an address that you can send to that will be automatically forwarded through the appropriate webform.
Sunlight has some spam-checking to stop this from being abused, and gathers some of the other information the forms collect so that they can be fully populated by the scripts. Once you're setup in the system, you can email "email@example.com" and your message will automatically be forwarded on to you senators and house reps.
88% of Congressional staffers say that their bosses' decisions are affected by constituent email. The data and scripts are up on Github for you to build on.
We finally gave Congress email addresses
But we just wanted to be able to email our representatives like normal people. So now, if you visit a legislator's page on OpenCongress, you'll see an email address in the right-hand sidebar that looks like Sen.Reid@opencongress.org or Rep.Boehner@opencongress.org. You can also email firstname.lastname@example.org to email both of your senators and your House representatives at once.
The first time we get an email from you, we'll send one back asking for some additional details. This is necessary because our code submits your message by navigating those aforementioned congressional webforms, and we don't want to enter incorrect information. But for emails after the first one, all you'll have to do is click a link that says, "Yes, I meant to send that email."
One more thing: For now, our system will only let you email your own representatives. A lot of people dislike this. We do, too. In an age of increasing polarization, party discipline means that congressional leaders must be accountable to citizens outside their districts. But the unfortunate truth is that Congress typically won't bother reading messages from non-constituents — that's why those zip code requirements exist in the first place. Until that changes, we don't want our users to waste their time.