Client Emails - best way to track and file?

Any one have a good system for tracking / filing Client emails? I use Yahoo and was thinking of moving client emails into custom folders you can create in the email program, then backing up somehow. Is this the best way to do this?

THanks All.

Thats basically how I do it for my sidework. I have a folder assigned for each client and I can easily access them whenever I need to. Granted, I use gmail, but I imagine yahoo would function the same way. I do similar with my outlook account at work. I archive to separate folders for each category that I work on. It is set to automatically archive every month or so.

Thanks Joyride: Can you set it to archive to your harddrive?? THX.

I don’t use webmail. It’s slow and annoying. Get a desktop email client. Can read without internet connection after you’ve downloaded. Easy to set up with Yahoo. Windows? Try Thunderbird.