Most filtering of unsolicited automated mail (aka "spam" or "junk mail") is handled by a spam filter before those mail messages reach your Inbox. This filtering helps to reduce the amount of spam that is put in your Inbox.
In addition to the automatic ZCS spam filtering rules, you can setup your mail preferences to identify specific addresses to block or not block in your Inbox. You create a list of addresses that should not be added to your Inbox and addresses that always should be added to your Inbox, but could be detected as spam. The spam filter uses this list to make sure you get the email you expect.
In the Block messages from area, specify email addresses from certain senders that should always be treated as spam.
In the Allow messages from area specify email addresses of people you trust so that their messages are not sent to your Spam folder. Messages from these email addresses are never blocked. You do not need to add all your trusted addresses to this list. Add addresses to this list that for some reason end up in your Spam folder and you do not want them there, such as newsletters you subscribe to.
Go to Preferences and select Mail.
On the page that opens, scan to the Spam Mail Options section.
Enter complete email addresses in the appropriate boxes, either Block messages from or Allow messages from. You can enter up to 100 addresses for each.
Click Save on the toolbar.