Managing my e-mail

Some weeks I am away from home.  I keep up with my email via a rather dumb SquirrelMail web interface (provided by my ISP), and delete the spam.  But I wish I could organise it!  When I go home, I connect to the net, and my mail client downloads the email.  Then I have to go through it a second time and stuff it in the right folders and generally clear it up.  This takes time that I badly need for other purposes.

I wish that there was a better way.  Ideally I could organize it via the web, and then download it pre-organized.  Any suggestions, anyone?