Contrary to popular opinion, there is not a law that says you must answer every e-mail as it is received. In fact, this is a sure-fire way to kill your productivity and end up becoming a slave to e-mail rather than using it as a tool to accomplish your work on your terms. One simple way to do this is to schedule specific times of day to work on e-mail.
The most unproductive thing you can do when it comes to e-mail is to read the same messages over and over again. This has the effect of doubling, tripling, or even quadrupling your workload. Instead, you should read each message once, then decide what to do with it. Read-decide. Read-decide. This is the pattern of effective e-mail processing. The goal is to end up with an empty inbox daily or, at the very least, every couple of days.