Believe it or not, some politicians even make a genuine effort to represent the concerns of their constituents. Anyway, politicians pay a lot of attention to their mail. That means that your letter represents the opinion of six hundred voters. If you get four other people to write, your politician sees three thousand votes. That's a lot of votes.
Votes are very important to politicians.
Unfortunately, you have got to snailmail it. Most politicians don't have email, and even if they do, they get as much spam as the next user. Your thoughts will count more if you send them on real paper made of dead trees in a real envelope. So send them paper. Tell your friends to send them paper.