As no-one has responded yet, here's my 2 cents worth:
(although I'm sure you have looked through Google).
1. Why is the Blocked Senders List limited to 500?http://blogs.earthlink.net/webmail/2006/11...ited_to_500.php
2. Rules and tools to filter junk mail - (see e.g. the spambayes filter)http://www.slipstick.com/rules/junkmail.asp
Most spam is sent from a different address every time.
The safe and blocked lists can hold a total of about 2000 addresses between them -
you could easily fill it up in a day or two by blocking addresses and domains.
It's better to set junk email to high, add addresses to the safe list
and check the junk mail folder often.
Ensure you are using the 'International' settings as required.
The blocked senders list should have just a few addresses on it, many times fewer than the safe list.
The blocked senders list is of limited use;
most spammers fake the FROM address and change it regularly.
Understanding the Safe and Blocked Senders listshttp://www.slipstick.com/rules/safesenders.htm
"Microsoft imposed the limit to improve performance";
whilst Registry keys could be altered to increase the limit, this would be self-defeating.
Hope you get a response from regular users of Outlook 2003, I mainly use OE.