For you GTD followers out there, this a good article regarding how often you should check your email and the factors your should consider. This is something I use to battle but have a pretty good routine now. I typically check it once in the morning about an hour after I get to work and then triage it throughout the day. I will then process it to zero before going home for the day. I use the hour when I first get to work to deal with any outstanding issues that might have occured overnight. I have found that this works fairly well for me. Some days might differ slightly depending on what is going on, but as a general rule I try to follow this.