If you have a POP3 email account, there is a simpler way of preventing porn getting into your inbox than using rules in your client. Go to
http://www.mailwasher.net
and have a look at mailwasher, there is extensive tutorials and assistance available there. I use it to preprocess all my mail, it downloads the headers and classifies the mail for you, it is extremely simple to set up and use, it works with dial up/broadband/network connections and any email client including Outlook Express/Outlook/Eudora etc. The one thing to note is that you should set your email client NOT to check the mail on a regular basis, leave it upto mailwasher. I have OE set up to download the mail when launched and at no other time. I never launch OE, I launch mailwasher, it checks the mail and when it has finished it then launches OE. The only time the Send/Receive button is used is to send mail, the little down arrow next to the Send/Receive button on the toolbar.
It is completely free, but you can send a donation to the author so that he can continue development.
Have a look, it took me about 2 minutes to set it up after having a quick glance at the tutorial and I now wouldn't be without it.
Geoff