Via Drudge I saw an article about Bill Clinton only sending two emails during his presidency, but the story misses the likely reason. Presidential emails sent from government computers (i.e., all the computers in the White House) would be public records and available for any interested party to read. Under those circumstances, I wouldn't write email either. I've also heard that President Bush's legal counsel advised him to stop using email when he became president.
It's possible that both presidents use(d) secret, personal computers to send private emails, but there's not really any way to know that for sure.
"I've also heard that President Bush's legal counsel advised him to stop using email when he became president."
Exactly right. When Bush took office I remember reading the sign-off email he sent to friends and family explaining why he would no longer use email. Any email he sent or received could be subpeoaned, and rather than risk revealing private conversations he chose to abandon email entirely. I expect all future presidents will follow the same policy.