I check my work email 3 times/day. Once in the morning, after lunch, and before quitting for the day. Since my email is on another box and I check it through an RDP session, it's easy to follow my rules. After I started following this schedule my productivity has gone up A LOT. At first I worried I would miss something important like a server going down, but if there is an emergency I ended getting a phone call anyways.
Dealing with work IM is my next productivity project. It was okay when it was just the developers, but as my role has expanded so has my IM list. I've thought about just turning it off, but I want to remain available to the SVPs who ask rare, but usually important questions. I may just select all the PMs and block them :p