1. From e-mail from sender that you want to filter, copy the e-mail address. Highlight the From: line and <ctrl-c> to copy.
2. From the Desktop or Mailbox, on the menu at the top of the screen, click on Edit menu --> Preferences
3. Click on the tab called Messaging and them make sure you are on the page called Mail Rules:
4. At the bottom of the window you will find a box titled "Junk mail handling:" Click on the drop down menu and change the setting to "Accept". The default is to "Delete Silently" but sometimes it will delete mail you want. It's better to change it to Accept and set up rules to deal with specific kinds of junk mail.
5. To create a rule, click on the box on top right called Mailbox Rules (red arrow above). Fill in rule as shown below and paste the e-mail address into the right box. You will have to clean up the "name" and < and > from the address for it to work properly. You can set many different kinds of rules using the If, Then. When done with the rule, click on <Save>.
You can create as many rules as you want. You may find it helpful to route mail to a specific folder.