I just managed to screw up my mailspool for 24 hours after playing with my .procmailrc and getting the regular expression wrong and putting all my important mail in a hardly read folder...
That is not the embarassing part though... after attempting to fix it I managed to send all of my mail to a folder I never read, I thought things had been quite today on the lists that I am on!
Anyhow the lesson to be learned is that procmail is very powerful but when given to someone who thinks that they know what they are doing it becomes a very dangerous weapon!
If you don't know what procmail is then I guess I should let you know as it is very useful (unless you think you know it all and break it!) anyhow procmail will filter you email into seperate folders so that you can (for example) read all of the alug posts at the same time while they don't get mixed in with your normal email!
I currently have about 10 different folders for different mailing lists, as I am following so many topics ranging from beginners python programming all the way to info about my car.
Take a look at http://www.procmail.org/ for the full package, it is a very useful tool even if you can be a complete muppet (like me) and get it *SO* wrong because you didn't read the warnings on the box.
Adam