A litle more info would be useful such as the e-mail you use. Most web based mail (which i'm assuming that's what it is) allows you to access your account through a mail prog such as netscape messenger. If you did this then you could download all mail messages to your hard disk and free up some space.
Alternatively create another free e-mail account and forward messages that you want to keep to free up space. It's not great but does free up space. I do this at the moment as I'm not always in the same place, and may need to access old e-mails while still having enough room to receive new ones.
Select all the text within the e-mail, copy it to the clip board. Then open up a new notepad file and paste the text currently in the clip board to the blank notepad window.
Then save the notepad file to floppy or Hard disk.
You could also use Wordpad, its a bigger file, but will stop it from looking like an old speccy effort.