Do you use Mozilla Thunderbird? If not, I highly recommend it. If you do, here’s a tip:
Compact your folders periodically. You can do this by clicking File –> Compact Folders. You can also right-click on a folder and select “Compact this folder”. I think Thunderbird automatically compacts folders if you select “Empty Trash”, but if you’re like me, I rarely ever empty the trash. Instead, I manually delete messages out of there, leaving certain messages just in case I discover I need them.
Why should you compact folders? When you delete a message in Thunderbird it doesn’t actually get removed from the files that hold all your e-mail on the hard drive. It’s marked as deleted and doesn’t show up. When you compact folders it removes all of the deleted e-mails. As you can imagine, this can be quite the problem if you get tons of e-mail and never compact your folders.
Example: every so often my friend noted that Thunderbird had to re-build the inbox. It would take about 15 minutes each time. I investigated and his e-mail was taking up 2.75 GB (yes, gigabytes)! After compacting folders the size of his e-mail is now only 190 MB!! How’s that for saving hard drive space? Not to mention the time it saves not waiting 10-20 minutes for his inbox to re-build!