Like with many BB users, spam is the daily curse.

Email filters for specific addresses work well, but I want to filter an entire domain. I've RTFM'd and it says I can use the asterisk as a wildcard.

But if I create a filter like *@xyz.com it seems to have no effect.

What syntax is required to block a whole domain?

Try *xyz.com

I'm using just the domain, with no leading @ symbol, like this:

ebay.com
microsoft.com

This has been working fine for me.

Agree with UncleMike. Even @domain.com will work, as this is how I have them set. Just include as much of the address in the filter as you need, but no more.

I actually like this^ way better, as it specifically refers to the domain. With the way I described it's possible it might match any domain that ends with the specified string. For example, specifying "ebay.com" might also match "abcdebay.com".