I advice you to remove all the shortcuts of mail clients and browsers from the quickLaunch bar, desktop and system tray.
It really worked for me in my case: I struggled with instant messenger addiction a couple months ago. I just removed it's shortcut from quicklaunch bar. So next time when I wanted to launch the IM, I found out that I just felt too lazy to look for .exe file somewhere in my hard drive.
So instead of starting it every time I connected to internet, I started my instant messenger only when I really needed to talk to someone.