McCain
Sen. McCain's war injuries make it difficult and painful to lift his arms and sustain that position of working on any keyboard.
Additionally, it has been said any number of times that the least effective way to reach a member of government is to write them an email. They prefer snail mail that is not anonymous, so they can use it as evidence for support or denial of an issue. Letters delivered by post are strong currency in Washington.
Finally, members of congress seldom read their own email, nor do they respond to it. that is a staff job.
Summary: consider McCain's medical reasons for not using email. And writing emails to Washington is not an effective way to communicating with your representative, particularly anonymously, since those are the first that are deleted. It would be far better to call your senate or congressional district regional office, to make your voice heard.