If you're using SpamAssassin, you can also use the blacklist_from option in its config file.

For SpamAssasin, the * is just a regular wildcard, not a regular expression. You need to include the @ or you'll exclude all mail from any domain ending in ...lan.com, not just lan.com. For multiple domains, just use multiple blacklist_from lines.

This works by adding a very large value (100) to the spam score, so it will get filed according to how you're sorting your mail that's tagged as spam.

BTW, you can include special characters like ^ or :p without them being translated by checking the "Disable smilies in text" option in the "Additional Options" box below the submit/preview buttons.