As someone who has run a small ISP, I can personally testify to just how easy it is to eavesdrop on e-mail without even intending to.  I don't know that writing a congressman would do much immediate good -- the issue is primarily technical.  Getting and consistently using a good encryption package [like PGP] would be a much more effective strategy.  And, be sure to *read* and *understand* how that package works.  Encryption is one of those things that, if not properly used, can actually make you (and those you communicate with) *less* secure, not more.

Cheers!