For the very reason that email can be very dangerous to an employee who uses it frivolously, it can be equally beneficial to an employee who uses it wisely. Use an email as confirmation of agreements you reach about compensation or promotion. Use an email to confirm positive feedback about your performance. Use an email to confirm complaints you have raised about issues that arise at work to protect you from retaliation.
Remember, a verbal conversation is easily denied or reconstructed. An email, electronically dated and time stamped, stands on its own merit. Finally, do take as much care in writing one as you would in sending a letter to your friends or family members. You never know who may be reading your emails, and for what purpose they may be used, in the future.