One option is to clear out some of the spam addresses and block by domain as opposed to user. For example, if you see multiple spam emails coming from Yahoo.com.hk, and you haven't any Yahoo contacts using a Hong Kong Yahoo account, go into the Block Addresses, delete all the applicable individual addresses and just add the domain (ie: yahoo.com.hk). You can recover room in the block list that way.
Below are some other hints that you can apply as best practices to help minimize the spam. Unfortunately no one product is foolproof but maybe some of the suggestions below may help.
===================
You shouldn't open unsolicted email from unknown sources. Often what happens is that when you open up spam, it sends back a trigger to the originating source indicating that a valid email address has been found thus subjecting you to even more spam down the road. Even using the preview pane in email products sends web beacons back to spammers.( http://helpdesk.gwu.edu/mailfilter/spam.html )
Here are a few steps you can take to try and avoid spam.
1. Don't open unsolicited Spam. Often what happens is that when you open up spam, it sends back a trigger to the originating source indicating that a valid email address has been found thus subjecting you to even more spam down the road.
2. Don't use the Preview Pane for the same reasons as #1. Also adjust your email options not to automatically open up email messages. Set it so that after you finish reading one email and take the necessary action you return to the inbox and not open the next one.
3. Set you email options to accept mail from only people in your address book or safe lists.
4. Set some filters to automatically route spam to certain folders for easy deletion later.
5. Use a throwaway account for any online registrations you need such as news sites and contests, etc. Often these email addresses are sold to other places, particularly advertising firms. If the throwaway account gets over run, you can simply delete it and create another.
6. Use the BCC when composing emails and encourage your friends to do the same. What this does is protects mailing lists from email harvesters.
7. You can consider using a third party application such as SpamFighter (free version can only be used for 1 account and it is for Outlook and Outlook Express only) http://www.spamfighter.com/ . Mailwasher is also a good antispam tool. http://www.mailwasher.net/
8. Never reply to any spam email that you happen to open and receive for the same reason as #1 above.
You can see more info at the webpage below:
http://www.us-cert.gov/cas/tips/ST04-007.html